A basket contains green, black and blue balls in the ratio 5:2:1. If there are 10 blue balls, find the new ratio when 10 green and 10 black balls are removed.
Worked solution (try it first)
Blue is 1 part and there are 10 blue balls, so one part is 10 balls: 50 green, 20 black and 10 blue.
Remove 10 green and 10 black: 40 green, 10 black and 10 blue are left.