5/6, 7/18, 5/9, 2/72

a. determine the lcd of the above by inspection. lcd by inspection

b. determine the lcd of the above by division of prime numbers. lcd by division of prime numbers

a. LCD by inspection:

Write the multiples and take a consideration to 72,

6 = 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 72, 78

18 = 0, 18, 36, 54, 72, 90

9 = 9, 18, 27, 36, 45, 54, 63, 72, 81

72 = 0, 72, 144,

So if we observe the lowest common multiple is 72.

b. LCD by division of prime numbers

Write the factors of the denominators 6, 18, 9, 72

6 = 2 x 3

18 = 2 x 3 x 3

9 = 3 x 3

72 = 2 x 2 x 2 x 3 x 3

The LCD = 2 x 2 x 2 x 3 x 3 = 72