Question

Determine if the following are in proportion: $15,45,40,120$

Answer 1

We have,

$15,45,40,120$

$\begin{array}{rcl}\mathrm{Ratio}\mathrm{of}15\mathrm{to}45& =& \frac{15}{45}\\ & & \mathrm{Dividing}\mathrm{numerator}\mathrm{and}\mathrm{denominator}\mathrm{by}15\\ & =& \frac{1}{3}\\ & =& 1:3\end{array}$

$\begin{array}{rcl}\mathrm{Ratio}\mathrm{of}40\mathrm{and}120& =& \frac{40}{120}\\ & & \mathrm{Dividing}\mathrm{numerator}\mathrm{and}\mathrm{denominator}\mathrm{by}40\\ & =& \frac{1}{3}\\ & =& 1:3\end{array}$

Since, $15:45=40:120$

Hence, $15,45,40,120$ are in proportion.