Question

If the first, second, and fourth terms of a proportion are $3,11$ and $55$ respectively, find the third term.

Answer 1

Let, the third term be $\mathrm{X}$, then

$3˸11\colon\colon \mathrm{X}˸55$

Product of extremes $=$ Product of means

$\begin{array}{rcl}3\times 55& =& 11\times \mathrm{X}\\ \mathrm{X}& =& \frac{3\times 55}{11}\\ \mathrm{X}& =& 15\end{array}$

Hence, the third term is $15$