Prime Factorization Math Example 2

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Example 2

hard
Use prime factorization to find gcdโก(180,252)\gcd(180, 252) and lcm(180,252)\text{lcm}(180, 252).

Solution

  1. 1
    Factor 180=22ร—32ร—5180 = 2^2 \times 3^2 \times 5 and 252=22ร—32ร—7252 = 2^2 \times 3^2 \times 7.
  2. 2
    gcdโก\gcd: take the minimum exponent for each shared prime: 2minโก(2,2)ร—3minโก(2,2)=22ร—32=4ร—9=362^{\min(2,2)} \times 3^{\min(2,2)} = 2^2 \times 3^2 = 4 \times 9 = 36.
  3. 3
    lcm\text{lcm}: take the maximum exponent for each prime that appears: 22ร—32ร—5ร—7=36ร—35=1,2602^2 \times 3^2 \times 5 \times 7 = 36 \times 35 = 1{,}260.
  4. 4
    Verify: gcdโกร—lcm=36ร—1,260=45,360=180ร—252\gcd \times \text{lcm} = 36 \times 1{,}260 = 45{,}360 = 180 \times 252. โœ“

Answer

gcdโก(180,252)=36\gcd(180, 252) = 36; lcm(180,252)=1,260\text{lcm}(180, 252) = 1{,}260.
Prime factorization reveals the GCD and LCM simultaneously. GCD uses minimum exponents (shared factors only); LCM uses maximum exponents (all factors). The relationship gcdโกร—lcm=aร—b\gcd \times \text{lcm} = a \times b is a useful check.

About Prime Factorization

Writing a whole number as a product of prime numbers; every composite number has exactly one such representation (up to order).

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