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

$\dfrac{TN}{TS} = \dfrac{MN}{RS}$

$\dfrac{1}{2} = \dfrac{MN}{2b-2a}$

$2MN = 2b - 2a$

$MN = b - a$

Answer: b - a