Question

Determine, if the following are in proportion:

$5,7,40,56$

Answer 1

For ratio in proportion:

If $a:b::c:d$,

$\frac{a}{b}=\frac{c}{d}$

We have $ad=bc$

Consider the proportion, $5:7::40:56$

Product of extremes is $5\times 56=280$

Product of means is $7\times 40=280$

Thus, product of extremes is equal to product of means.

Hence, $5,7,40,56$ are in proportion.