NCERT Solutions for Class 11 Science Computer science Chapter 5 - Getting Started With Python

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) 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 a hyphen ( - ).

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

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

Answer:

a) ( 0 == (1==2))

b) (2 + (3 == 4) + 5) == 7

c) (1 < -1) == (3 > 4 )

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.

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 ten-digit 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'}

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'.

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. 

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
 

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

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

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

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: ",num1-num2)
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

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.

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.

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

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

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

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

Answer:

The formula is given as:
E = mc²
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.

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.