1994 AMC 12 Problem 5

Attempt Problem 5 of the 1994 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 1994 AMC 12 solutions, or check the answer key.

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

5.

Pat intended to multiply a number by 66 but instead divided by 6.6. Pat then meant to add 1414 but instead subtracted 14.14. After these mistakes, the result was 16.16. If the correct operations had been used, the value produced would have been
less than 400400
between 400400 and 600600
between 600600 and 800800
between 800800 and 10001000
greater than 10001000
Answer: E
Concepts:reverse operationslinear equations
Small hint:
Undo the mistaken subtraction and division to recover the starting number
Big hint:
Apply 6x+146x+14 to that starting number
Solution:
If the starting number is x,x, the mistaken calculation gives x6−14=16, \frac{x}{6}-14=16, so x=180.x=180. The intended calculation would produce 6(180)+14=1094,6(180)+14=1094, which is greater than 1000.1000. Thus the correct answer is E.
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