Chapter 4.4, Problem 34STP

To determine

The number of miles she travelled at speed between 35 and 70 miles per hour.

Answer to Problem 34STP

Option B. 84 is correct.

Explanation of Solution

Given:

Ross family drove 300 miles. Mrs. Ross drove 70 miles per hour for 65% of the trip and 35 miles per hour or less for 20% of the trip that was left.

Mrs. Ross never went over 70 miles per hour.

Calculation:

65% of the distance is:

  $\begin{array}{l}65\%\times 300=0.65\left(300\right)\\ \text{ = 195}\end{array}$

20% of the remaining distance is:

  $\begin{array}{l}20\%\times \left(300-195\right)=0.2\left(105\right)\\ \text{ = 21}\end{array}$

The rest of the distance is:

  $300-195-21=84$

Hence, Option B. 84 is correct.