Question

Find the fourth proportional of 30, 32, 42

Answer 1

let the fourth proportional be x.
x = 32×42/30
x =44.8

Answer 2

a:b::c:d
30:32::42:d
30/32=42/d
then we will cross multiply
30×42=32×d
d=30×42/32
d=15×21/8
d= 315/8is the fourth proportional of 30,32,42