Question 987555

sarah is traveling from city A to b. the distance between these 2 cities is 185 miles and she planned to arrive at city b in 2 hrs 30 minutes. her average speed for the first 1 hr 40 minutes was 75 miles per hour. but then she realized she should slow down to dive more safely. if she still wanted to arrive at her destination on time , at what speed should she drive.
<pre>Driving for 1 hr 40 minutes at 75 mph means that she covered a distance of {{{75(1&2/3)}}}, or {{{75(5/3)}}}, or 125 miles
This means that she still has 60 (185 - 125) miles to cover in 50 minutes ({{{2&1/2 - 1&2/3}}}) hours, or {{{5/6}}} hour
Therefore, she has to drive at a speed of: {{{60/(5/6)}}}, or {{{60 * (6/5)}}}, or {{{highlight_green(72)}}} mph