Question

check whether 7,21,3,9 are in proportion

Answer 1

yes it is in proportion since
7*9=63 and also 21*3=63 therfore this numbers are in proportion

Answer 2

We have,

7:21 = 1 :3

And,

3 : 9 = 1: 3

Therefore, 7:21 = 3 :9

So, 7: 21 : : 3 : 9