CSET Multiple Subjects Subtest 2: Math and Science Practice Test 2026 - Free Math and Science Practice Questions and Study Guide

The greatest common divisor is the largest number that divides both numbers. To find it, break each number into prime factors:

48 = 2^4 × 3, and 180 = 2^2 × 3^2 × 5. The common prime factors are 2 and 3, and you take the smallest powers they appear with in both factorizations: 2^2 and 3^1. Multiply those together to get 2^2 × 3 = 4 × 3 = 12.

So 12 is the largest number that divides both 48 and 180 (and you can verify: 48 ÷ 12 = 4 and 180 ÷ 12 = 15).