2010 AMC 8 Problem 22

Attempt Problem 22 of the 2010 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 2010 AMC 8 solutions, or check the answer key.

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22.

The hundreds digit of a three-digit number is 22 more than the units digit. The digits of the three-digit number are reversed, and the result is subtracted from the original three-digit number. What is the units digit of the result?
0 0
2 2
4 4
6 6
8 8
Answer: E
Concepts:place valuedigits
Small hint:
The tens digit cancels when the reversed number is subtracted.
Big hint:
Represent the original number with hundreds digit two more than the units digit.
Solution:
Let the units digit be u,u, and let the tens digit be t.t. This makes the hundreds digit be u+2.u+2. This makes the number equal to 100(u+2)+10t+u100(u+2) +10t+u=101u+200+10t=101u+200+10t and the reversed number is 100u+10t+(u+2)100u +10t+(u+2)=101u+2+10t.=101u+2+10t. This makes the difference equal to (101u+10t+200)−(101u+10t+200)-(101u+10t+2)=198.(101u+10t+2)=198. This makes the units digit 8.8.
Therefore, the answer is E .
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