Question

Point M belongs to AN , point N belongs to BM , AB = 18 in and AM : MN : NB = 1:2:3. Find MN.

Answer 1

MN = 6 in

add the parts of the ratio, 1 + 2 + 3 = 6

divide AB by 6 to find 1 part of the ratio

$\frac{18}{6}$ = 3 ← 1 part

AM = 3 in ← 1 part

MN = 2 × 3 = 6 in ← 2 parts

NB = 3 × 3 = 9 in ← 3 parts

and 3 + 6 + 9 = 18 in = AB