Question

The ratio of rock music to total CDs that ella owns is 25/40. Paolo has 50 rock music CDs. The ratio of rock music to total CDs in hos collection is equivalent to the ratio of rock music to total CDs in ella's collection. How many CDs do they own?

Answer 1

They own a total of 120 CDs.

GIVEN:
Ella: ratio of rock music to total CDs that she owns 25/40
Paolo: has 50 rock music CDs. The ratio of rock music to total CD is equal to Ella's ratio.

Proportion: a/b = c/d where ad = bc

25/40 = 50/x
25x = 40 * 50
25x = 2000
25x / 25 = 2000 / 25
x = 80  total of Paolo's CDs

Total of Ella's CDs       =  40
Total of Paolo's CDs   =  80
Total CDs in all               120