# Class 11 Computer Science Chapter 4 Introduction to Problem Solving NCERT Solution

### Chapter 4 Introduction to Problem Solving

1. Write pseudocode that reads two numbers and divide one by another and display the quotient.

2. Two friends decide who gets the last slice of a cake by flipping a coin five times. The first person to win three flips wins the cake. An input of 1 means player 1 wins a flip, and a 2 means player 2 wins a flip. Design an algorithm to determine who takes the cake?

3. Write the pseudocode to print all multiples of 5 between 10 and 25 (including both 10 and 25).

4. Give an example of a loop that is to be executed a certain number of times.

5. Suppose you are collecting money for something. You need `200 in all. You ask your parents, uncles and aunts as well as grandparents. Different people may give either` 10, `20 or even` 50. You will collect till the total becomes 200. Write the algorithm.

6. Write the pseudocode to print the bill depending upon the price and quantity of an item. Also print Bill GST, which is the bill after adding 5% of tax in the total bill.

7. Write pseudocode that will perform the following:
a) Read the marks of three subjects: Computer Science, Mathematics and Physics, out of 100
b) Calculate the aggregate marks
c) Calculate the percentage of marks

8. Write an algorithm to find the greatest among two different numbers entered by the user.

9. Write an algorithm that performs the following:
Ask a user to enter a number. If the number is between 5 and 15, write the word GREEN. If the number is between 15 and 25, write the word BLUE. if the number is between 25 and 35, write the word ORANGE. If it is any other number, write that ALL COLOURS ARE BEAUTIFUL.

10. Write an algorithm that accepts four numbers as input and find the largest and smallest of them.

11. Write an algorithm to display the total water bill charges of the month depending upon the number of units
consumed by the customer as per the following criteria:
• for the first 100 units @ 5 per unit
• for next 150 units @ 10 per unit
• more than 250 units @ 20 per unit
Also add meter charges of 75 per month to calculate the total water bill .

12. What are conditionals? When they are required in a program?

13. Match the pairs

14. Following is an algorithm for going to school or college. Can you suggest improvements in this to include other options?
Reach_School_Algorithm
a) Wake up
c) Take lunch box
d) Take bus
e) Get off the bus
f) Reach school or college

15. Write a pseudocode to calculate the factorial of a number ( Hint: Factorial of 5, written as 5! =5 × 4× 3× 2×1) .

16. Draw a flowchart to check whether a given number is an Armstrong number. An Armstrong number of three digits is an integer such that the sum of the cubes of its digits is equal to the number itself. For example, 371 is an Armstrong number since 33 + 73 + 1**3 = 371.

17. Following is an algorithm to classify numbers as “Single Digit”, “Double Digit” or “Big”.
Classify_Numbers_Algo
INPUT Number
IF Number < 9
“Single Digit”
Else If Number < 99
“Double Digit”
Else
“Big”

Verify for (5, 9, 47, 99, 100 200) and correct the algorithm if required

18. For some calculations, we want an algorithm that accepts only positive integers upto 100.

Accept_1to100_Algo
INPUT Number
IF (0<= Number) AND (Number <= 100)
ACCEPT
Else
REJECT

a) On what values will this algorithm fail?
b) Can you improve the algorithm?

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