Question

A private jet flies the same distance in 11 hours that a commercial jet flies in 5 hours. If the speed of the commercial jet was 128 mph less than 3 times the speed of the private jet, find the speed of each jet.

Answer 1

Let speed of private be x, then speed of commercial jet is,

$3x-128$

The same distance travelled by private jet in 11 hours and by commercial plane is 5 hours. So equation for same distance is,

$11\cdot x=5(3x-128)$

Solve the equation for x.

$\begin{gathered} 11x=15x-640 \\ 640=15x-11x \\ x=\frac{640}{4} \\ =160 \end{gathered}$

Determine the speed of commercial jet.

$\begin{gathered} 3\cdot160-128=480-128 \\ =352 \end{gathered}$

So speed of private jet is 160 mph and speed of commercial jet is 352 mph.