The ratio of blue marbles to yellow marbles in a jar is 7 to 9. If there are 28 blue marbles in the jar, how many yellow marbles are there?
There are 36 yellow marbles.
proportion: a:b = c:d where ad = bc
7:9 = 28:x
7x = 928
7x = 252
7x/7 = 252/7
x = 36
7:9 = 28:36
736 = 9*28
252 = 252
Ratio: 7:9
Blue marbles to yellow marbles.
28 blue marbles
74 = 28
94 = 36
28:36
Answer: There are 36 yellow marbles