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| Math Central | Quandaries & Queries |
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Question from joan, a teacher: How many positive divisors of ((2^20)*(5^20))^2 are less than (2^20)*(5^20) but do not divide (2^20)*(5^20)? |
Joan,
It is the number where the exponent of 2 is between 21 and 40 OR the exponent of 5 is between 21 and 40. This is the number where the exponent of 2 is as described (between 21 and 40) plus the number where the exponent of 5 is as described, minus the number where both exponents are as described. This is 20x41 + 20x41 - 20x20.
Victoria
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