Question

Find a in the following proportions:- 3,a,5,20

Answer 1

they are in proportion
hence
$\frac{x}{y} = \frac{z}{w}$
$\frac{3}{a} = \frac{5}{20} \\ a = \frac{20 \times 3}{5} \\ a = 12$
Hope this helps you.

Answer 2

Product of mean = product of ecreme

a*5= 3*20

a= 60/5

a=12