How many positive integer divisors… | GMAT Quant Solution
Question
How many positive integer divisors does 8! have?
- 14
- 15
- 24
- 56
- 96
Topics: factorials, prime factorization, divisibility
Solution
Step 1
We prime factorize 8! by expressing each integer factor from 1 to 8 in its prime form
8! = 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1
Step 2
We combine like prime factors by summing their exponents
8! = (2^3) × 7 × (2 × 3) × 5 × (2^2) × 3 × 2 × 1 = 2^7 × 3^2 × 5^1 × 7^1
Step 3
We count the number of positive divisors by adding one to each exponent and multiplying
(7+1) × (2+1) × (1+1) × (1+1) = 8 × 3 × 2 × 2 = 96
Answer
96 (E)
