math
posted by lidia on .
The total capacity of 2 water bottles, A and B, is 680 ml. The ratio of bottle A's capacity to bottle B's capacity is 4:6. How much larger is bottle B's capacity than bottle A's?
My answer is 136, am i right?

a + b = 680
a/b = 2/3
2 b = 3 a
a = (2/3) b
so
(2/3) b + b = 680
(5/3 ) b = 680
b = 408
then a = (2/3)408 = 272
then b  a = 136 ml