Question

A jet plane has 180,000 pounds of fuel after the first hour of flight. The four engines consume a total of 15,000 pounds per hour at its cruising altitude. How many pounds of fuel remain after the 8th hour?

Answer 1

After one hour of flight the plane has 180,000 pounds of fuel, since it consumes a total of 15,000 per hour, then we need to subtract 15,000 per hour it'll spend flying after the first one. From the 1st hour to the 8th, there are a total of 7 hours, so we need to multiply the consumption of fuel per hour by 7, then subtract the result from 180,000.

`\begin{gathered} \text{fuel}(8th)=180,000-7\cdot15,000 \\ \text{fuel}(8th)=180,000-105,000 \\ f\text{uel(}8th)=75,000 \end{gathered}`

A total of 75000 will remain after the 8th hour.