Question

find thefourth proportional to 4,16,and 18

Answer 1

let the fourth proportional no.be x.
then,4:16: :18:x
4*x=16*18
x=16*18/4
=4*18
=72
so it is 4:16: :18:72

Answer 2

4,16,18,x
4/16=18/x
so 4x=16*18
4x=288
x=72