Question

In a proportion, the $1st,2nd$ and $4th$ terms are $51,68$ and $108$ respectively. Find the $3rd$ term.

Answer 1

$\begin{array}{c}51:68::x:108\\ \frac{51}{68}=\frac{x}{108}\\ x=\frac{3\times 108}{4}=81\end{array}$