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2021 AMC 12A Question 5

AMC12 · 2021 AMC 12A

Question 5

When a student multiplied the number $66$ by the repeating decimal $$
1.\overline{ab} = 1.ababab\ldots,
$$ where $a$ and $b$ are digits, he did not notice the notation and just multiplied $66$ by the terminating decimal $1.ab.$ Later he found that his answer was $0.5$ less than the correct answer.

What is the two-digit integer $\overline{ab}?$
  1. $15$
  2. $30$
  3. $45$
  4. $60$
  5. $75$