AlgebraMediumTwo-digit number from its digits
Algebra practice question
The digits of a two-digit number add up to 9, and the number is 27 more than the number formed by reversing its digits. What is the number?
Answer: 63
With tens digit a and units digit b, a + b = 9 and (10a + b) − (10b + a) = 27, so a − b = 3. Then a = 6, b = 3 and the number is 63.
Common wrong answers
- If you answered 36
- 36 is the reversed number.
- If you answered 54
- 54 has digits summing to 9 but differs from 45 by 9.
- If you answered 72
- 72 has digits summing to 9 but differs from 27 by 45.
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