Class 9 Mathematics Chapter 11: The World of Algorithms — practice questions with answers
Free practice for Class 9 Mathematics, Chapter 11: The World of Algorithms. Try the solved questions below, then take a free test with instant marking and explanations.
56 questions16 easy, 26 medium, 14 hardNCERT · CBSE · State boards
Sample questions with solutions
Q1. In mathematics, what is meant by an algorithm?
- A precise step-by-step procedure to arrive at an answer
- A type of number
- A random guess
- A drawing tool
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Answer: A. A precise step-by-step procedure to arrive at an answer
Why: The column addition method is an algorithm. [p.37]
Why: The column addition method is an algorithm. [p.37]
Q2. In the column addition algorithm, why must the numbers be aligned from right to left?
- So that units are added to units, tens to tens and so on
- So the answer looks neat
- Because numbers are read from right to left
- It does not matter
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Answer: A. So that units are added to units, tens to tens and so on
Why: Place value groups are added separately. [p.37–39]
Why: Place value groups are added separately. [p.37–39]
Q3. If you count one dot per second, about how many seconds does it take to count the dots for 33 + 27?
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Answer: 60 (± 0)
Why: 60 dots → 60 seconds = 1 minute. [p.39]
Why: 60 dots → 60 seconds = 1 minute. [p.39]
Q4. Taking 15 seconds to add each column of digits, about how many seconds does it take to add two 4-digit numbers?
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Answer: 60 (± 0)
Why: 4 columns × 15 s = 60 s. [p.39]
Why: 4 columns × 15 s = 60 s. [p.39]
Q5. What is the gcd (greatest common divisor) of two numbers?
- The largest number that divides both
- The smallest number both divide
- Their product
- Their difference
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Answer: A. The largest number that divides both
Why: Also called hcf. [p.39]
Why: Also called hcf. [p.39]
Q6. Run the algorithm ‘for each j from 1 to 18, add j to the list if j divides 18’. What list is produced?
- [1, 2, 3, 6, 9, 18]
- [2, 3, 6, 9]
- [1, 18]
- [1, 2, 3, 4, 6, 9, 18]
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Answer: A. [1, 2, 3, 6, 9, 18]
Why: Listed in increasing order. [p.40–41]
Why: Listed in increasing order. [p.40–41]
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Frequently asked questions
How many practice questions are there for Class 9 Mathematics Chapter 11: The World of Algorithms?
56 questions (16 easy, 26 medium, 14 hard). A few are solved on this page; the free test shows the answer and explanation for every question after you submit.
Is this chapter from the NCERT book?
Yes — it follows the NCERT Class 9 Mathematics syllabus, used by CBSE and many state boards.