1993 AMC 8 Problem 21 — Solution | LIVE by Po-Shen Loh

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1993 AMC 8 Problem 21

Attempt Problem 21 of the 1993 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 1993 AMC 8 solutions, or check the answer key.

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

21.

If the length of a rectangle is increased by $20\%$ and its width is increased by $50\%,$ then the area is increased by

$10\%$

$30\%$

$70\%$

$80\%$

$100\%$

Answer: D

Concepts:percentage

Difficulty rating: 820

Solution:

The new length is $1.2$ times the old and the new width is $1.5$ times the old, so the new area is $1.2 \times 1.5 = 1.8$ times the old area.

That is an increase of $80\%.$

Thus, the correct answer is D .

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