Question

There are n gallons of oil. After m gallons have been used then, in terms of m and n, what percent of oil remains? What percent was used?

Answer 1

The percent of oil remains is
`(n-m)/(n) * 100 \%`

The percent used was
`(m)/(n) * 100 \%`

Solution:

Given that, there are n gallons of oil.

After m gallons have been used then, in terms of m and n

To find what percent was used:

`\text { percent of oil used }=\frac{u s e d \text { oil }}{\text { initial oil }} * 100 \%`

`\begin{array}{l}{\text { Percent of oil used }=\frac{m \text { gallons of oil }}{\text { n gallons of oil }} * 100} \\\\ {\rightarrow \text { per cent of oil used }=(m)/(n) * 100 \%}\end{array}`

To find what percent of oil remains:

`\begin{array}{l}{\text { Now, percent of oil remaining }=100 \% \text { - percent of oil used }} \\\\ {\rightarrow \text { percent of oil remaining }=100 \%-(m)/(n) * 100 \%} \\\\ {\rightarrow \text { percent of oil remaining }=100 \%\left(1-(m)/(n)\right)} \\\\ {\rightarrow \text { percent of oil remaining }=100 \% * (n-m)/(n)} \\\\ {\text { So, percent of oil remaining is } (n-m)/(n) * 100 \%}\end{array}`