CBSE Class 10 Mathematics Standard sample paper 2025-26: question 19
From the official CBSE sample question paper for 2025-26, section A, question 19, for 1 mark. Try it first; the hints and our step-by-step solution are below.
Q19 · 1 mark · Assertion-reasonCompetency-basedReal Numbers
Assertion (A): The number cannot end with the digit 0, where n is a natural number
Reason (R): A number ends with 0, if its prime factorization contains both 2 and 5
- (A)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A)
- (B)Both assertion (A) and reason (R) are true and reason (R) is not the correct explanation of assertion (A)
- (C)Assertion (A) is true but reason (R) is false.
- (D)Assertion (A) is false but reason (R) is true.
Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2025-26.
Hints
Open one hint at a time and try again before the next.
Hint 1
What must a number be divisible by to end in 0?
Hint 2
Write down the prime factorisation of .
Step-by-step solution
Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.
Reason (R) is true: a number ends in 0 only if it is divisible by 10 = 2 × 5, so its prime factorisation must contain both 2 and 5.
- 1 mark
has only the prime 5 in its factorisation and no 2, so by uniqueness of prime factorisation it cannot end in 0. Hence (A) is true and (R) explains it, which is option (A).
Answer: Option (A)
Where the marks are
- Recognises that has no factor 2, so (A) is true and explained by (R), option (A) (1 mark)
Revise the chapter
- Chapter: Real Numbers (notes, formulas, where marks are lost and every past question)
- Topic: Fundamental Theorem of Arithmetic
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