Question

The time required to deliver and install a computer at a customer's location is t= 4 + d over r, where t is time in hours, d is the distance, in miles, from the warehouse to the customer's location, and r is the average speed of the delivery truck. If it takes 6.2 hours for the employee to deliver and install a computer for a customer located 100 miles from the warehouse, what is the average speed of the delivery truck?

Answer 1

$t=4+\frac{d}{r} \\ \\ t=6.2 \ [h] \\ d=100 \ [miles] \\ \\ 6.2=4+\frac{100}{r} \\ 6.2-4=\frac{100}{r} \\ 2.2=\frac{100}{r} \\ 2.2r=100 \\ r=\frac{100}{2.2} \\ r=45 \frac{5}{11} \\ r \approx 45.45 \ [\frac{miles}{h}]$

The average speed of the delivery truck is about 45.45 miles per hour.