Question

Find the forth proportional to 42,12,7

Answer 1

let the fourth ratio is. x
so we can write it now. 42:12:7:x
and then. 42/12::7/x
then we doing cross multiply
42x = 12*7
x =2

Answer 2

Answer:

Let the forth proportional be x

Then,= 42 : 12 :: 7 : x

        = 42 * x = 12 * 7

        = 42 * x = 84

        = x = 84/42

        = x = 2