2006 AMC 8 Problem 11

Attempt Problem 11 of the 2006 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 2006 AMC 8 solutions, or check the answer key.

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

11.

How many two-digit numbers have digits whose sum is a perfect square?
1313
1616
1717
1818
1919
Answer: C
Concepts:digitsperfect squarecasework
Small hint:
The largest possible digit sum is 1818.
Big hint:
Count the two-digit numbers whose digit sums are 1,1, 4,4, 9,9, and 1616.
Solution:
There is 11 number whose digit sum is 11: 10.10.
There are 44 numbers whose digit sum is 44: 13,13, 22,22, 31,31, and 40.40.
There are 99 numbers whose digit sum is 99: 18,18, 27,27, 36,36, 45,45, 54,54, 63,63, 72,72, 81,81, and 90.90.
There are 33 numbers whose digit sum is 1616: 79,79, 88,88, and 97.97.
Therefore, there are 1717 numbers that satisfy the problem statement.
Thus, C is the correct answer.
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