Question

fiurth propertion of 7 , 9 and 21

Answer 1

as we know that

when four numbers are in proportion then the product of end terms is equal to product of mean terms

let forth term be x

so

7x=9×21

x=9×21/7

x=27

so the forth proportion is 27

Answer 2

Let number be x
7:9::21:x
x=27(7×3=21therefore 9×3=27)