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Page No 115:
Question 1:
Which of the following identifier names are invalid and why?
i

Serial_no.

v

Total_Marks

ii

1st_Room

vi

totalMarks

iii

Hundred$

vii

_Percentage

iv

Total Marks

viii

True

Answer:
i) Serial_no.: Invalid  Identifier in python cannot contain any special character except underscore(_).
ii) 1st_Room: Invalid  Identifier in Python cannot start with a number.
iii) Hundred$: Invalid  Identifier in Python cannot contain any special character except underscore(_).
iv) Total Marks: Invalid  Identifier in Python cannot contain any special character except underscore(_). If more than one word is used as a variable then it can be separated using underscore ( _ ), instead of space.
v) Total_Marks: Valid
vi) totalMarks: Invalid  Identifier in Python cannot contain any special character except underscore(_). If more than one word is used as a variable then it can be separated using underscore ( _ ), instead of a hyphen (  ).
vii) _Percentage: Valid
viii) True: Invalid  Identifier in Python should not be a reserved keyword.
Page No 115:
Question 2:
Write the corresponding Python assignment statements:
a) Assign 10 to variable length and 20 to variable breadth.
b) Assign the average of values of variables length and breadth to a variable sum
c) Assign a list containing strings ‘Paper’, ‘Gel Pen’, and ‘Eraser’ to a variable stationery.
d) Assign the strings ‘Mohandas’, ‘Karamchand’, and ‘Gandhi’ to variables first, middle and last.
e) Assign the concatenated value of string variables first, middle and last to variable fullname. Make sure to incorporate blank spaces appropriately between different parts of names.
Answer:
a) length, breadth = 10,20
b) sum = (length + breadth)/2
c) stationary =['Paper','Gel Pen','Eraser']
d) first,middle,last = "Mohandas","Karamchand","Gandhi"
e) fullname = first +" "+ middle +" "+ last
Page No 115:
Question 3:
Write logical expressions corresponding to the following statements in Python and evaluate the expressions (assuming variables num1, num2, num3, first, middle, last are already having meaningful values):
a) The sum of 20 and –10 is less than 12.
b) num3 is not more than 24
c) 6.75 is between the values of integers num1 and num2.
d) The string ‘middle’ is larger than the string ‘first’ and smaller than the string ‘last’
e) List Stationery is empty
Answer:
a) (20 + (10)) < 12
b) num3 <= 24 or not(num3 > 24)
c) (6.75 >= num1) and (6.75 <= num2)
d) (middle > first) and (middle < last)
e) len(Stationery) == 0
Page No 116:
Question 4:
Add a pair of parentheses to each expression so that it evaluates to True.
a) 0 == 1 == 2
b) 2 + 3 == 4 + 5 == 7
c) 1 < 1 == 3 > 4
Answer:
a) ( 0 == (1==2))
b) (2 + (3 == 4) + 5) == 7
c) (1 < 1) == (3 > 4 )
Page No 116:
Question 5:
Write the output of the following.
a) num1 = 4
num2 = num1 + 1
num1 = 2
print (num1, num2)
b) num1, num2 = 2, 6
num1, num2 = num2, num1 + 2
print (num1, num2)
c) num1, num2 = 2, 3
num3, num2 = num1, num3 + 1
print (num1, num2, num3)
Answer:
a) 2, 5
b) 6, 4
c) Error as num3 is used in RHS of line 2 (num3, num2 = num1, num3 + 1) before defining it earlier.
Page No 116:
Question 6:
Which data type will be used to represent the following data values and why?
a) Number of months in a year
b) Resident of Delhi or not
c) Mobile number
d) Pocket money
e) Volume of a sphere
f) Perimeter of a square
g) Name of the student
h) Address of the student
Answer:
a) The int data type will be used to represent 'Number of months in a year' as it will be an integer i.e. 12.
b) The boolean data type will be used to represent 'Resident of Delhi or not' as a person will be either a resident of Delhi or not a resident of Delhi. Therefore, the values True or False will be sufficient to represent the values.
c) The integer data type will be used to represent 'Mobile number' as it will be a tendigit integer only.
d) The float data type will be used to represent 'Pocket money' as it can be in decimal. e.g Rs. 250.50 i.e 250 rupees and 50 paise.
e) The float data type will be used to represent 'Volume of a sphere'.
The formula for the volume of a sphere:
$\mathrm{Volume}\mathrm{of}\mathrm{sphere},\mathrm{V}=\frac{4}{3}{\mathrm{\pi r}}^{3}$
Even if 'r' is a whole number, the value of volume can be a fraction which can be represented in a decimal form easily by float data type.
f) The float data type will be used to represent 'Perimeter of a square'.
The perimeter of a square:
Perimeter = 4 × side length
If the side length is a decimal number, the result may come out to be a decimal number which can be easily represented by float data type.
Note: If the side length is a whole number, the perimeter will always be an integer, however, we should be open to the possibility that the side length can be in decimal as well.
g) The string data type will be used to represent 'Name of the student'.
h)The string data type will be used to represent 'Address of the student'. However, if we have to store the address in a more structured format, we can use dictionary data type as well. e.g. Address = { 'Line1': ‘Address line 1', 'Line2':'Address Line2', 'Locality':'Locality Name', 'City':'City Name', 'Pincode':110001, 'Country':'India'}
Page No 116:
Question 7:
Give the output of the following when num1 = 4, num2 = 3, num3 = 2
a) num1 += num2 + num3
print (num1)
b) num1 = num1 ** (num2 + num3)
print (num1)
c) num1 **= num2 + num3
d) num1 = '5' + '5'
print(num1)
e) print(4.00/(2.0+2.0))
f) num1 = 2+9*((3*12)8)/10
print(num1)
g) num1 = 24 // 4 // 2
print(num1)
h) num1 = float(10)
print (num1)
i) num1 = int('3.14')
print (num1)
j) print('Bye' == 'BYE')
k) print(10 != 9 and 20 >= 20)
l) print(10 + 6 * 2 ** 2 != 9//4 3 and 29>= 29/9)
m) print(5 % 10 + 10 < 50 and 29 <= 29)
n) print((0 < 6) or (not (10 == 6) and (10<0)))
Answer:
a) num1 += 3 + 2
The above statement can be written as
num1 = num1 + 3 + 2 = 4 + 3 + 2 = 9
Therefore, print(num1) will give the output 9.
b) num1 = num1 ** (num2 + num3)
The above statement will be executed as per the following steps.
num1 = 4 ** (3 + 5) = 4 ** 5 = 1024
Therefore, print(num1) will give the output 1024.
c) num1 **= num2 + num3
The above statement can be written as
num1 **= 5
num1 = num1 ** 5
num1 = 4 ** 5
num1 = 1024
Therefore, the output will be 1024.
d) num1 = '5' + '5'
The RHS in the above statement is '5' + '5'. Please note that 5 is enclosed in quotes and hence will be treated as a string. Therefore, the first line is just a string concatenation which will give the output 55. The type of output will be a string, not an integer.
e) print(4.00/(2.0 + 2.0))
The numbers written in the statement are in float data type therefore, the output will be also in float data type.
print(4.00/(2.0 + 2.0))
print(4.0/4.0)
1.0
Therefore, the output will be 1.0.
f) num1 = 2 + 9 * ((3 * 12)  8) /10
# The expression within inner brackets will be evaluated first
num1 = 2 + 9 * (36  8) /10
# The expression within outer brackets will be evaluated next
num1 = 2 + 9 * 28/10
# * and / are of same precedence, hence, left to right order is followed
num1 = 2 + 252/10
num1 = 2 + 25.2
num1 = 27.2
Therefore, the output will be 27.2.
g) num1 = 24 // 4 // 2
#When the operators are same, left to right order will be followed for operation
num1 = 6 // 2
#When floor division is used, return value will be int data type
num1 = 3
Therefore, the output will be 3
h) num1 = float(10)
float(10) will convert integer value to float value and therefore, the output will be 10.0.
i) num1 = int('3.14')
This will result in an error as we cannot pass string representation of float to an int function.
j) print('Bye' == 'BYE')
As Python compares string character to character and when different characters are found then their Unicode value is compared. The character with lower Unicode value is considered to be smaller. Here, 'y' has Unicode 121 and 'Y' has 89. Therefore, the output will be 'False'.
k) print(10 != 9 and 20 >= 20)
print(True and True)
print(True)
Therefore, the output will be 'True'.
l) print(10 + 6 * 2 ** 2 != 9//4 3 and 29>= 29/9)
Taking the above statement in two separate parts
LHS:
10 + 6 * 2 ** 2 != 9//4  3
10 + 6 * 4 != 2  3
10 + 24 != 1
34 != 1
True
RHS:
29 >= 29/9
True
Now the complete equation can be written as
print(True and True)
Therefore, the output will be 'True'.
m) print(5 % 10 + 10 < 50 and 29 <= 29)
Taking the above statement in two separate parts
LHS :
5 % 10 + 10 < 50
5 + 10 < 50
15 < 50
True
RHS:
29 <= 29
True
Now, the complete equation can be written as
print(True and True)
Therefore, the output will be 'True'.
n) print( (0 < 6) or (not (10 == 6) and (10<0) ) )
print(True or (not False and False))
print(True or (True and False))
# not will be evaluated before and/or.
print(True or False)
print(True)
Therefore, the output will be 'True'.
Page No 117:
Question 8:
Categorise the following as syntax error, logical error or runtime error:
a) 25 / 0
b) num1 = 25; num2 = 0; num1 / num2
Answer:
a) Runtime Error. The syntax for the division is correct. The error will arise only when 'interpreter' will run this line.
b) Runtime Error. The syntax is correct. The error will arise only when 'interpreter' will run the line containing these statements.
Page No 117:
Question 9:
A dartboard of radius 10 units and the wall it is hanging on are represented using a twodimensional coordinate system, with the board’s centre at coordinate (0,0). Variables x and y store the xcoordinate and the ycoordinate of a dart that hits the dartboard. Write a Python expression using variables x and y that evaluates to True if the dart hits (is within) the dartboard, and then evaluate the expression for these dart coordinates:
a) (0,0)
b) (10,10)
c) (6, 6)
d) (7,8)
Answer:
The distance formula can be used to calculate the distance between the points where the dart hits the dartboard and the centre of the dartboard.
The distance of a point P(x, y) from the origin is given by $\sqrt{{x}^{2}+{y}^{2}}.$
To calculate the square root, the equation can be raised to the power 0.5.
Program:
x = int(input('Enter X Coordinate: '))
y = int(input('Enter Y Coordinate: '))
dis = (x ** 2 + y ** 2) ** 0.5
#if dis is greater than 10, means that dart is more than 10 units away from the centre.
print(dis <= 10)
The output for the dart coordinates are as follows:
a) (0,0): True
b) (10,10): False
c) (6,6): True
d) (7,8): False
Page No 117:
Question 10:
Write a Python program to convert temperature in degree Celsius to degree Fahrenheit. If water boils at 100 degree C and freezes as 0 degree C, use the program to find out what is the boiling point and freezing point of water on the Fahrenheit scale. (Hint: T(°F) = T(°C) × 9/5 + 32)
Answer:
Program:
#defining the boiling and freezing temp in celcius
boil = 100
freeze = 0
print('Water Boiling temperature in Fahrenheit::')
#Calculating Boiling temperature in Fahrenheit
tb = boil * (9/5) + 32
#Printing the temperature
print(tb)
print('Water Freezing temperature in Fahrenheit::')
#Calculating Boiling temperature in Fahrenheit
tf = freeze * (9/5) + 32
#Printing the temperature
print(tf)
OUTPUT:
Water Boiling temperature in Fahrenheit::
212.0
Water Freezing temperature in Fahrenheit::
32.0
Page No 117:
Question 11:
Write a Python program to calculate the amount payable if money has been lent on simple interest.
Principal or money lent = P, Rate of interest = R% per annum and Time = T years. Then Simple Interest (SI) = (P x R x T)/ 100.
Amount payable = Principal + SI. P, R and T are given as input to the program.
Answer:
Program:
#Asking the user for Principal, rate of interest and time
P = float(input('Enter the principal: '))
R = float(input('Enter the rate of interest per annum: '))
T = float(input('Enter the time in years: '))
#calculating simple interest
SI = (P * R * T)/100
#caculating amount = Simple Interest + Principal
amount = SI + P
#Printing the total amount
print('Total amount:',amount)
OUTPUT:
Enter the principal: 12500
Enter the rate of interest per annum: 4.5
Enter the time in years: 4
Total amount: 14750.0
Page No 118:
Question 12:
Write a program to calculate in how many days a work will be completed by three persons A, B and C together. A, B, C take x days, y days and z days respectively to do the job alone. The formula to calculate the number of days if they work together is xyz/(xy + yz + xz) days where x, y, and z are given as input to the program.
Answer:
Program:
#Asking for the number of days taken by A, B, C to complete the work alone
x = int(input('Enter the number of days required by A to complete work alone: '))
y = int(input('Enter the number of days required by B to complete work alone: '))
z = int(input('Enter the number of days required by C to complete work alone: '))
#calculating the time if all three person work together
#formula used as per the question
combined = (x * y * z)/(x*y + y*z + x*z)
#rounding the answer to 2 decimal places for easy readability
days = round(combined,2)
#printing the total time taken by all three persons
print('Total time taken to complete work if A, B and C work together: ', days)
OUTPUT:
Enter the number of days required by A to complete work alone: 8
Enter the number of days required by B to complete work alone: 10
Enter the number of days required by C to complete work alone: 20
Total time taken to complete work if A, B and C work together: 3.64
Page No 118:
Question 13:
Write a program to enter two integers and perform all arithmetic operations on them.
Answer:
Program:
#Program to input two numbers and performing all arithmetic operations
#Input first number
num1 = int(input("Enter first number: "))
#Input Second number
num2 = int(input("Enter second number: "))
#Printing the result for all arithmetic operations
print("Results:")
print("Addition: ",num1+num2)
print("Subtraction: ",num1num2)
print("Multiplication: ",num1*num2)
print("Division: ",num1/num2)
print("Modulus: ", num1%num2)
print("Floor Division: ",num1//num2)
print("Exponentiation: ",num1 ** num2)
OUTPUT:
Enter first number: 8
Enter second number: 3
Results:
Addition: 11
Subtraction: 5
Multiplication: 24
Division: 2.6666666666666665
Modulus: 2
Floor Division: 2
Exponentiation: 512
Page No 118:
Question 14:
Write a program to swap two numbers using a third variable.
Answer:
Program:
#defining two variables
x = 5
y = 6
#printing the values before swapping
print("The values of x and y are",x,"and",y,"respectively.")
# k is the third variable used to swap values between x and y
k = x
x = y
y = k
#printing the values after swapping
print("The values of x and y after swapping are",x,"and",y,"respectively.")
OUTPUT:
The values of x and y are 5 and 6 respectively.
The values of x and y after swapping are 6 and 5 respectively.
Page No 118:
Question 15:
Write a program to swap two numbers without using a third variable.
Answer:
Program:
#defining two variables
x = 5
y = 6
#printing the values before swapping
print("The values of x and y are",x,"and",y,"respectively.")
# Using 'multiple assignment' to swap the values
x,y = y,x
#printing the values after swapping
print("The values of x and y after swapping are",x,"and",y,"respectively.")
OUTPUT:
The values of x and y are 5 and 6 respectively.
The values of x and y after swapping are 6 and 5 respectively.
Page No 118:
Question 16:
Write a program to repeat the string ''GOOD MORNING'' n times. Here 'n' is an integer entered by the user.
Answer:
The string will be repeated only if the value is greater than zero, otherwise, it will return a blank. Therefore, ‘if’ condition will be used to check the values of 'n' first and then the print statement will be executed.
Program:
str = "GOOD MORNING "
n = int(input("Enter the value of n: "))
if n>0:
print(str * n)
else:
print("Invalid value for n, enter only positive values")
OUTPUT:
Enter the value of n: 5
GOOD MORNING GOOD MORNING GOOD MORNING GOOD MORNING GOOD MORNING
Page No 118:
Question 17:
Write a program to find average of three numbers.
Answer:
Program:
#defining three variables
a = 5
b = 6
c = 7
#calculating average using the formula, average = (sum of variables)/(number of variables)
average = (a + b + c)/3
#print the result
print("The average of",a,b,"and",c,"is",average)
OUTPUT:
The average of 5 6 and 7 is 6.0
Page No 118:
Question 18:
The volume of a sphere with radius r is 4/3πr^{3}. Write a Python program to find the volume of spheres with radius 7 cm, 12 cm, 16 cm, respectively.
Answer:
Program:
#defining three different radius using variables r1, r2, r3
r1 = 7
r2 = 12
r3 = 16
#calculating the volume using the formula
volume1 = (4/3*22/7*r1**3)
volume2 = (4/3*22/7*r2**3)
volume3 = (4/3*22/7*r3**3)
#printing the volume after using the round function to two decimal place for better readability
print("When the radius is",r1,"cm, the volume of the sphere will be", round(volume1,2),"cc")
print("When the radius is",r2,"cm, the volume of the sphere will be", round(volume2,2),"cc")
print("When the radius is",r3,"cm, the volume of the sphere will be", round(volume3,2),"cc")
OUTPUT:
When the radius is 7 cm, the volume of the sphere will be 1437.33 cc
When the radius is 12 cm, the volume of the sphere will be 7241.14 cc
When the radius is 16 cm, the volume of the sphere will be 17164.19 cc
Page No 118:
Question 19:
Write a program that asks the user to enter their name and age. Print a message addressed to the user that tells the user the year in which they will turn 100 years old.
Answer:
Program:
#Program to tell the user when they will turn 100 Years old
name = input("Enter your name: ")
# age converted to integer for further calculation
age = int(input("Enter your age: "))
#calculating the 100th year for the user considering 2020 as the current year
hundred = 2020 + (100  age)
#printing the 100th year
print("Hi",name,"! You will turn 100 years old in the year",hundred)
OUTPUT:
Enter your name: John
Enter your age: 15
Hi John ! You will turn 100 years old in the year 2105
Page No 118:
Question 20:
The formula E = mc^{2} states that the equivalent energy (E) can be calculated as the mass (m) multiplied by the speed of light (c = about 3×10^{8} m/s) squared. Write a program that accepts the mass of an object and determines its energy.
Answer:
The formula is given as:
E = mc^{2}
where, E ⇒ energy measured in Joule,
m ⇒ mass in Kilogram,
c ⇒ speed of light in m/s.
Program:
#Program to calculate the equivalent energy of an object
#asking for the mass in grams
mass = float(input("Enter the mass of object(in grams): "))
#Speed of light is known and given in the question
c = 3 * 10 ** 8
#calculating the energy, mass is divided by 1000 to convert it into kilogram
Energy = (mass/1000) * c ** 2
#printing the output
print("The energy of an object with mass",mass," grams is",Energy,"Joule.")
OUTPUT:
Enter the mass of object(in grams): 25
The energy of an object with mass 25.0 grams is 2250000000000000.0 Joule.
Page No 118:
Question 21:
Presume that a ladder is put upright against a wall. Let variables length and angle store the length of the ladder and the angle that it forms with the ground as it leans against the wall. Write a Python program to compute the height reached by the ladder on the wall for the following values of length and angle:
a) 16 feet and 75 degrees
b) 20 feet and 0 degrees
c) 24 feet and 45 degrees
d) 24 feet and 80 degrees
Answer:
The diagram can be drawn as follows:
Here:
sin($\theta $) = height / length
⇒ height = length × sin($\theta $)
To calculate the sin() value in Python, math module sin() function is needed. The values need to be passed in radians to the sin() function. Therefore, the degree will be converted to radians and then the sin() function will be applied.
Program:
#import the math module, to use sin & radians function
import math
length = int(input("Enter the length of the ladder: "))
degrees = int(input("Enter the alignment degree: "))
#Converting degrees to radian
radian = math.radians(degrees)
#Computing sin value
sin = math.sin(radian)
# Calculating height and rounding it off to 2 decimal places
height = round(length * sin,2)
#displaying the output
print("The height reached by ladder with length",length,"feet and aligned at",degrees,"degrees is",height, "feet.")
OUTPUT:
a) Enter the length of the ladder: 16
Enter the alignment degree: 75
The height reached by the ladder with length 16 feet aligned at 75 degrees is 15.45 feet.
b) Enter the length of the ladder: 20
Enter the alignment degree: 0
The height reached by the ladder with length 20 feet and aligned at 0 degrees is 0.0 feet.
c) Enter the length of the ladder: 24
Enter the alignment degree: 45
The height reached by the ladder with length 24 feet and aligned at 45 degrees is 16.97 feet.
d) Enter the length of the ladder: 24
Enter the alignment degree: 80
The height reached by the ladder with length 24 feet and aligned at 80 degrees is 23.64 feet.
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