How many distinct pairs of consecutive positive integers have a product that is less than 1000?
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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 3 1 × 3 2 = 9 9 2 is the largest such pair and 1 × 2 = 2 is the smallest.
Therefore, we have ( 1 , 2 ) , … , ( 3 1 , 3 2 ) ⇒ 3 1 pairs.