Question

Ben, Jerry and Kumar had some flour. The ratio of the amount of flour Ben had to the amount of flour Jerry had was 2:3. Jerry had 4/5 the amount of flour Kumar had. Kumar had 420 g of flour more than Ben. How much flour did Jerry have?

1) 240 g
2) 630 g
3) 720 g
4) 840 g

Answer 1

B/J = 2/3
J/K = 4/5
K = B + 420

well B= 2 J / 3
and K = 5 J/4
so
5 J / 4 = 2 J / 3 + 420
15 J / 12 - 8 J / 12 = 420
7 J = 420 * 12
J = 720