Betty drives for a number of hours at 70 miles per hour. When traffic slows, she drives at 50 miles per hour. She travels at 50 miles per hour for 0.5 hours longer than she traveled at 70 miles per hour. The difference between the distance traveled at 50mph and 70mph is 5 miles. Determine how long Betty traveled at 50 miles per hour.

Question

kendricklamar2014 · Answer

let 
x = time in hours travelled at 70 mph 

$$70x = d $$

$$50(x + .5) = di $$

$$di - d = 5 $$

$$50(x + .5) - 70x = 5 $$
$$50x + 25 - 70x = 5 $$
$$-20x = -20 $$
$$x = 1 $$

she travelled for 1 + .5 = 

1.5 hours at 50 mph 
1 hour at 70 mph