Question

Samuel had some coins. The number of ten cent coins was 2/5 the number of twenty cent coins. Samuel took out 10 twenty cent coins from the bag and exchanged them for ten cent coins of equal value. The ratio of the number of ten cent coins to the number of twenty cent coins became 8/5. How many twenty cent coins and ten cent coins did he have at first?

Please help, thanks so much.

Answer 1

If there are x 10¢ coins and y 20¢ coins, then what do you know?
x = 2/5 y
after the switch, then
(x+20)/(y-10) = 8/5
(2/5 y + 20)/(y-10) = 8/5
2y+100 = 8y-80
now finish it off