1989 AMC 8 Problem 18
Attempt Problem 18 of the 1989 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 1989 AMC 8 solutions, or check the answer key.
All problems are used with official legal permission of the Mathematical Association of America (MAA).
18.
A calculator has a reciprocal key that replaces the number currently displayed with its reciprocal. For example, if the display shows and the key is pressed, the display becomes If is currently displayed, what is the fewest number of times the reciprocal key must be pressed so that the display again reads
Small hint:
Pressing the key once turns into
Big hint:
The reciprocal of the reciprocal of a number is the number itself
Solution:
Pressing the key once changes to its reciprocal
Pressing it a second time takes the reciprocal again, returning to So presses are enough.
Thus, the correct answer is B .
Problem 18 in other years
- 1985 AMC 8
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