1990 AMC 8 Problem 6

Attempt Problem 6 of the 1990 AMC 8 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 1990 AMC 8 solutions, or check the answer key.

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

6.

Which of these five numbers is the largest?
13579+1246813579 + \dfrac{1}{2468}
13579−1246813579 - \dfrac{1}{2468}
13579×1246813579 \times \dfrac{1}{2468}
13579÷1246813579 \div \dfrac{1}{2468}
13579.246813579.2468
Answer: D
Concepts:fraction
Small hint:
Dividing by 12468\dfrac{1}{2468} is the same as multiplying by 24682468
Big hint:
All the other choices stay near 1357913579, but one of them becomes thousands of times larger
Solution:
Choices A, B, and E are all very close to 1357913579, and choice C multiplies 1357913579 by a tiny number, making it much smaller.
Choice D divides by 12468\dfrac{1}{2468}, which is the same as multiplying by 24682468. This makes it thousands of times larger than 1357913579, so it is the largest.
Thus, the correct answer is D .
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