UKMT - Junior Kangaroo - 2023 - 13 | Exact Science

13

How many pairs of two-digit positive integers have a difference of 50?

A. 10

B. 20

C. 25

D. 35

E. 40

Answer

E. 40

SOLUTIOn

The smallest pair of two-digit integers with a difference of 50 is 10 and 60. The largest pair of two-digit integers with a difference of 50 is 49 and 99. Hence there are 40 pairs of two-digit integers with a difference of 50.

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