Question

In the figure, M and N are midpoints of RT and ST. What is the length of MN?

a. a + b
b. b - a
c. 2

I think it's B. What do you think?

Answer 1

Length RS = 2b - 2a

Given that N is the midpoint of TS
⇒ Ratio of TN : TS = 1 : 2


`(TN)/(TS) = (MN)/(RS)`


`(1)/(2) = (MN)/(2b-2a)`


`2MN = 2b - 2a`


`MN = b - a`

Answer: b - a