SOLUTION: 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

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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.
Found 2 solutions by josgarithmetic, MathTherapy:
Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
             speed        time          distance
FAST          75        1%262%2F3           d%5Bf%5D
SLOWER         r        t%5Bs%5D            d%5Bs%5D
Totals                  2%261%2F2             185


Four variables but not nearly as bad as it appears.

d%5Bf%5D=75%2A%285%2F3%29=125
and
t%5Bs%5D=2%261%2F2-1%262%2F3=5%2F2-5%2F3=%2815-10%29%2F6=5%2F6
and then
d%5Bs%5D=185-d%5Bf%5D=185-125=60

You should be able to find r.

Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!

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.
Driving for 1 hr 40 minutes at 75 mph means that she covered a distance of 75%281%262%2F3%29, or 75%285%2F3%29, or 125 miles

This means that she still has 60 (185 - 125) miles to cover in 50 minutes (2%261%2F2+-+1%262%2F3) hours, or 5%2F6 hour

Therefore, she has to drive at a speed of: 60%2F%285%2F6%29, or 60+%2A+%286%2F5%29, or highlight_green%2872%29 mph