Question

A, B, C and D are four points on a line such that AB:AC = 7:10, and BD:CD = 9:2. If CD = 9 cm, what is the length, in cm, of AB?
A) 49 B) 64 C) 54.25 D)73.25 E)70

Answer 1

Let
AB=7m
BC=3m
Now let
BC=7n
CD=2n
Now, CD=9, so n=9/2
BC=7*9/2 = 63/2 = 3m
so m = 21/2, making
AB = 7m = 7*21/2 = 147/2 = 73.5
Is there a typo, or did I make a mistake?

Answer 2

D should be 73.5, so you are correct