AC=4, AE=7, AD=10, what is the length of AB?
A: 1 3/7
B: 2 1/2
C: 5 5/7
D: 17 1/2

Answer:
C. [tex] AB = 5\frac{5}{7} [/tex]
Step-by-step explanation:
When two polygons are considered similar, the ratio of their corresponding sides would also be equal.
Since ∆ABC and ∆ADE are similar, [tex] \frac{AE}{AC} = \frac{AD}{AB} [/tex]
[tex] \frac{7}{4} = \frac{10}{AB} [/tex]
Cross multiply
[tex] 7*AB = 10*4 [/tex]
[tex] 7*AB = 40 [/tex]
Divide both sides by 7 to find AB
[tex] \frac{7*AB}{7} = \frac{40}{7} [/tex]
[tex] AB = \frac{40}{7} [/tex]
[tex] AB = 5\frac{5}{7} [/tex]