1990 AMC 8 Problem 13

Below is the professionally curated solution for Problem 13 of the 1990 AMC 8, 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.

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Concepts:rate floor and ceiling functions

Difficulty rating: 930

13.

One proposal for new postage rates for a letter was $30$ ¢ for the first ounce and $22$ ¢ for each additional ounce (or fraction of an ounce). The postage for a letter weighing $4.5$ ounces was

$96$ ¢

$1.07

$1.18

$1.20

$1.40

Solution:

The first ounce costs $30$ ¢. The remaining $3.5$ ounces are charged as $4$ additional ounces, since any fraction rounds up to a full ounce.

That is $4 \cdot 22$ ¢ $= 88$ ¢, so the total is $30$ ¢ $+ 88$ ¢ $= 118$ ¢ $= \$1.18.$

Thus, the correct answer is C .

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