Maths Olympiad Prep

Track / Stage 3 / 32 of 260 #32 of 1964

Problem 32

AMC 10/12, early questions
Number theory Difficulty 3.1 Multiple choice

The number of distinct positive integral divisors of (30)4(30)^4 excluding 11 and (30)4(30)^4 is

Pick one

Official solution

(Error compiling LaTeX. Unknown error_msg)The prime factorization of $30$ is $2\cdot3\cdot5$, so the prime factorization of $30^4$ is $2^4\cdot3^4\cdot5^4$. Therefore, the number of positive divisors of $30^4$ is $(4+1)(4+1)(4+1)=125$. However, we have to subtract $2$ to account for $1$ and $30^4$, so our final answer is $125-2=123, \boxed{\text{C}}

Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic, difficulty and ordering added by this site.