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2005 Alabama ARML TST Problems/Problem 6

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Problem

How many of the positive divisors of 3,240,000 are perfect cubes?

Solution

3240000=2^7\cdot 3^4\cdot 5^4. We want to know how many numbers are in the form 2^{3a}3^{3b}5^{3c} which divide 3,240,000. This imposes the restrictions 0\leq a\leq 2,0 \leq b\leq 1 and 0 \leq c\leq 1, which lead to 12 solutions and thus 12 such divisors.

See Also

2005 Alabama ARML TST (Problems)
Preceded by:
Problem 5
Followed by:
Problem 7
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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