Explanation

Find the prime factorization of 70

70 = 2 × 5 × 7

Find the prime factorization of 80

80 = 2 × 2 × 2 × 2 × 5

Multiply each factor the greater number of times it occurs in steps i) or ii) above to find the LCM:

LCM = 2 × 2 × 2 × 2 × 5 × 7

LCM = 560