Question

Find the value of ‘a’, given that 3,a,5,20 are in proportion.

Answer 1

$$\begin{gathered} 3,a,5,20areinproportion \\ 3:a::5:20 \\ \frac{3}{a}=\frac{5}{20} \\ a=\frac{3\times 20}{5} \\ a=3\times 4 \\ a=12 \end{gathered}$$