Question

Find the third proportion to $2.5$ and $8.5$

Answer 1

Step $1:$ To find the third proportion of $2.5$ and $8.5$

Let the third proportion to $2.5$ and $8.5$ be $x$

Then $2.5$$,$ $8.5$ and $x$ are in continued proportion$.$

i.e. $2.5:8.5::8.5:x$

Step $2:$ Now find the value of $x$

$\frac{2.5}{8.5}=\frac{8.5}{x}$

$2.5x=8.5\times 8.5$

$x=\frac{8.5\times 8.5}{2.5}$

$x=\frac{85\times 8.5}{25}$

$x=\frac{85\times 8.5}{5\times 5}$

$x=17\times 1.7$

$x=28.9$

Hence, the third proportion of $2.5$ and $8.5$ is $28.9$