2006 AMC 12A Problem 4

Attempt Problem 4 of the 2006 AMC 12A 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 2006 AMC 12A solutions, or check the answer key.

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

4.

A digital watch displays hours and minutes with AM and PM. What is the largest possible sum of the digits in the display?
1717
1919
2121
2222
2323
Answer: E
Concepts:digitsclock
Small hint:
Maximize the minutes digits and the hour digits separately
Big hint:
The two minutes digits sum to at most 5+9;5+9; the best hour is the single digit 99
Solution:
The two minutes digits sum to at most 5+9=14,5 + 9 = 14, at 5959 minutes past the hour. For the hour, a single digit 99 gives digit sum 9,9, which beats any two-digit hour (10,11,12(10, 11, 12 give at most 1+2=3).1 + 2 = 3).
The largest total is 14+9=23,14 + 9 = 23, occurring at 9 ⁣: ⁣59.9\!:\!59.
Thus, the correct answer is E.
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