Re: If n is a multiple of 15^2 x 20^3, which of the following is not
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17 Jul 2023, 05:41
15^2 x 20^3 can be prime factorised as 5^5 x 3^2 x 2^6. For choice A n/5000, 5000 can be factored as 5 x (5x2)^3 which is fully divisible by n, hence not correct. Choice B n/7500 7500 can be factored as 5^4 x 3^1 x 2^2 which is fully divisible by n, hence not correct. Choice C 3000/n^1/2, n is not a perfect square because 5 has an odd power hence the root of n will not be an integer. 3000/n^1/2 will not be an integer. Choice D follows similar logic, n^1/2 /200 will not be an integer. Choice E can be simplified to 1-n^3 , which will be a negative integer, hence not correct.
Answer: C,D