Difficulty: Easy
Correct Answer: 25/99
Explanation:
Introduction / Context:
Purely recurring decimals with a block of r digits convert to fractions whose denominator is r copies of 9. For 0.252525…, the repeating block is “25” with length r = 2.
Given Data / Assumptions:
Concept / Approach:
For x = 0.(AB) where AB is two digits, x = AB/99. Here AB = 25, hence x = 25/99 directly. This is a standard result from shifting the decimal by powers of 10 and subtracting to eliminate the repeat.
Step-by-Step Solution:
Let x = 0.252525…100x = 25.252525…Subtract: 100x − x = 25.2525… − 0.2525… = 25So 99x = 25 ⇒ x = 25/99.
Verification / Alternative check:
Compute 25 ÷ 99 ≈ 0.252525…, confirming the correct repeating block length and digits.
Why Other Options Are Wrong:
25/90 and 25/999, 25/9999 use incorrect denominators for a two-digit repeating block; 5/18 = 0.277… represents a single-digit repeating 7, not “25”.
Common Pitfalls:
Using 9, 99, 999 indiscriminately without matching the block length; forgetting that the decimal is purely repeating with no non-repeating prefix.
Final Answer:
25/99
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