ACT Math · Number operations and exponents

What is the prime factorization of 360?

What is the prime factorization of 360?

Answer and explanation

Answer: F: 2³ × 3² × 5

Divide by the smallest primes. 360=8⋅45=23⋅45360=8\cdot45=2^3\cdot45, and 45=9⋅5=32⋅545=9\cdot5=3^2\cdot5, so 360=23⋅32⋅5360=2^3\cdot3^2\cdot5, choice F. Check: 8⋅9⋅5=3608\cdot9\cdot5=360. Choice G (22⋅33⋅52^2\cdot3^3\cdot5) equals 540540, since the exponents of 22 and 33 are swapped. Choice H (23⋅3⋅522^3\cdot3\cdot5^2) equals 600600. Choice J (24⋅322^4\cdot3^2) equals 144144 and omits the factor of 55. A prime factorization must multiply back to the original number, which is the simplest check. Dividing repeatedly by 22, then 33, then 55 shows each prime factor in turn: 360,180,90,45,15,5,1360, 180, 90, 45, 15, 5, 1 uses three twos, two threes, and one five.

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