Question

ABC ~ DEF What is the value for x, the length of side BC?

Answer 1

Answer:

17.5

Step-by-step explanation:

as the triangles are similar, when oriented in the same direction they have the same angles, and the lengths of all sides of DEF are the lengths of the sides of ABC but multiplied by the same scaling factor f for all sides.

so, we see that

A ~ D

B ~ E

C ~ F

and therefore

AB ~ DE

BC ~ EF

CA ~ FD

that means

DE = AB × f

EF = BC × f

FD = CA × f

we know DE and AB.

so,

4 = 10 × f

f = 4/10 = 2/5

and now we know

EF = 7 = BC × f

BC = 7/f = (7/1) / (2/5) = (5×7)/(2×1) = 35/2 = 17.5