A truck driver started for his destination at an average speed of 70 miles per hour. Once snow began to fall, he had to drop his speed to 40 miles per hour. It took the driver 14 hours to reach his destination, which was 707 miles away. How many hours after the driver started did the snow begin to fall?
A) after $4.7 \mathrm{hr}$
B) after $4.9 \mathrm{hr}$
C) after $9.1 \mathrm{hr}$
D) after $9.3 \mathrm{hr}$

Question

Quizplus · Accepted Answer

Let $x$ be the time driven before the snow began to fall. The distance covered before the snow is $70x$ miles. The time driven after the snow began is $14-x$ hours, and the distance covered is $40(14-x)$ miles. The total distance is $70x + 40(14-x) = 707$. Solving for $x$, we get $x = 4.9$ hours.

A Truck Driver Started for His Destination at an Average 4.7hr4.7 \mathrm{hr}4.7hr

A Truck Driver Started for His Destination at an Average $4.7 \mathrm{hr}$