3 Answers

60

Your easiest way to determine is to list multiples of 15, as that is the largest of the three. You know 5 will work in all of THOSE because 15 is a multiple of 5. Since 4 is an even number, only the even numbered multiples of 15 may also be a multiple of  4

15, 30 (7 × 4 = 28, 8 × 4 = 32), 45, 60 (12 × 5, 15 × 4, 4 × 15)

 Find the prime factorization of these integers.

   4                 5                  15

  /  \                /   \                /  \

 2 • 2                  5              3 • 5

4  =  2 • 2  =  2^2

5   =       5  =   5^1

15  =  3 • 5  =  3^1 • 5^1

Starting with the highest exponent value, multiply...................

2^2 • 5^1 • 3^1

  4  •. 5  •  3  =  60

LCM  =  60