Difference between revisions of "2019 AMC 10A Problems/Problem 2"
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== Problem == | == Problem == | ||
What is the hundreds digit of <math>(20!-15!)?</math> | What is the hundreds digit of <math>(20!-15!)?</math> | ||
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| + | == Solution == | ||
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| + | The last three digit of <math>n!</math> for all <math>n>=15</math> is 000, because there are at least three 2s and three 5s in its prime factorization. Because <math>0-0=0</math>, The answer is <math>0</math>. | ||
Revision as of 15:14, 9 February 2019
Problem
What is the hundreds digit of 
Solution
The last three digit of 
for all 
is 000, because there are at least three 2s and three 5s in its prime factorization. Because 
, The answer is 
.
