Question

The ratio of Sally’s CDs to Ray’s CDs is 2: 7. Ray has 49 CDs. If Ray gives Sally 21 CDs, what will be the new ratio of Sally’s CDs to Ray’s?

Answer 1

Sally's CDs to Ray's CDs = 2:7
2 + 7 = 9
Ray's Cds to all CDs is 7:9

2x + 7x = 9x

2x + 49 = 9x

-7x = -49

x = 7

Ray has 7x = 49
Sally has 2x = 14

14:49 is the same as 2:7

Ray has 49 CDs. Sally had 14 CDs.
Ray gives 21 CDs to Sally.

Ray: 49 - 21 = 28
Sally: 14 + 21 = 35

Sally's CDs to Ray's CDs = 35:28 = 5:4