How do i find a scale factor?

In two similar geometric figures, the scale factor is the ratio of their corresponding sides, dividing the two corresponding lengths of the sides will gives the ratio, for example

What is the scale factor between 4 cm and 10 cm ?

4 and 10 are divisible by 2

Length A : 4 ÷ 2 = 2

Length B : 10 ÷ 2 = 5

so the scale factor from A to B is 2:5

12/11c

or

12

c

11

the answer is 13

step-by-step explanation:

5*5=25

12*12=144

25+144=169

169^2=13