Count Consecutive Carefully

How many distinct pairs of consecutive positive integers have a product that is less than 1000?


The answer is 31.

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1 solution

Danila Kurganov
Oct 20, 2019

As the product of these two positive integers must be less than 1000, we can find the maximum such pair, and count the number of remaining (smaller) pairs.

We see that 31 × 32 = 992 31 \times 32 = 992 is the largest such pair and 1 × 2 = 2 1 \times 2 = 2 is the smallest.

Therefore, we have ( 1 , 2 ) , , ( 31 , 32 ) 31 (1, 2), \dots , (31, 32) \Rightarrow 31 pairs.

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