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A student finds the average of 10, two–digit numbers. If the digits of one of the numbers is interchanged, the average increases by 3.6. The difference between the digits of the 2-digit numbers is
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- 4
- 3
- 2
- 5
- 4
Correct Option: A
According to question,
Total increase = 3.6 × 10 = 36
∴ If the number be 10p + q, then
Number obtained after reversing the digits = 10q + p
∴ 10q + p – 10p – q = 36
⇒ 9q – 9p = 36
⇒ 9 (q – p) = 36
⇒ q – p = 36 ÷ 9 = 4
