Question

4, *, 9, √13 are in proportion. Then * is

Answer 1

let * be x. if 4,x,9,√13 are in proportion then x(9)=4√13=>x=4√13/9 .Hope it helps you...

Answer 2

Let the * be b
4:b::9:√13
$\frac{4}{b} = \frac{9}{ \sqrt{13} } \\ 4 \sqrt{13} = 9b \\ b = \frac{4 \sqrt{13} }{9}$