1998 AMC 12 Problem 6

Attempt Problem 6 of the 1998 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1998 AMC 12 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

6.

If 19981998 is written as a product of two positive integers whose difference is as small as possible, then the difference is
88
1515
1717
4747
9393
Answer: C
Concepts:factorizationoptimization
Small hint:
Factor 19981998 and look for divisors near its square root
Big hint:
The closest factor pair is formed from 3737 and the remaining factor
Solution:
Since 1998=2⋅33⋅37,1998=2\cdot3^3\cdot37, its factor pair nearest 1998\sqrt{1998} is 37⋅54.37\cdot54. Their difference is 54−37=17,54-37=17, so C is correct.
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