In an 8hr day Mark can sell 15 flowers, Lou can sell 6 flowers and Cindy can sell 8 flowers. What is the smallest number of 8hr days needed for each of them to achieve the same number of sales?

Mark = 15 flowers

Lou = 6 flowers

Cindy = 8 hours

Find the Lowest common multiples

Method 1 (Simple but tedious):

15: 15, 30, 45, 60, 75, 90, 105, 120

6: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96, 104, 120

8: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88, 96, 104, 112, 120

Therefore:

15 x 8 = 120

6 x 20 = 120

8 x 15 = 120

Mark needs 8 8hrs

Lou needs 20 8hrs

Cindy needs 15 8hours

Method 2:

15 = 5 x 3

6 = 2 x 3

8 = 2 x 2 x 2

LCM = 2 x 2 x 2 x 3 x 5 = 120

120 : 15 = 8

120 : 6 = 20

120 : 8 = 15

Mark needs 8 8hrs

Lou needs 20 8hrs

Cindy needs 15 8hours