2017 AMC 8 Problems/Problem 19
Problem
For any positive integer , the notation
denotes the product of the integers
through
. What is the largest integer
for which
is a factor of the sum
?
Solution 1
Factoring out , we have
which is
Next,
has
factors of
. The
is because of all the multiples of
. Now
has
factors of
, so there are a total of
factors of
.
Solution 2
Also keep in mind that number of ’s in
is the same as the number of trailing zeros. Number of zeros is
means we need pairs of
’s and
’s; we know there will be many more
’s, so we seek to find number of
’s in
which solution tells us and that is
factors of
.
has
trailing zeros, so it has
factors of
and
.
Video Solution
https://youtu.be/HISL2-N5NVg?t=817
~ pi_is_3.14
~savannahsolver
See Also
2017 AMC 8 (Problems • Answer Key • Resources) | ||
Preceded by Problem 18 |
Followed by Problem 20 | |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | ||
All AJHSME/AMC 8 Problems and Solutions |
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