What was her average speed on Friday​?

Question

It took Ellen 2.7 hours to drive to her​ mother's house on Thursday morning. On her return trip on Friday night, traffic was​ heavier, so the trip took her 3 hours. Her average speed on Friday was 3 mph slower than on Thursday. What was her average speed on Friday​?

Answer 1

distance = rate of speed times time

d=rt r= speed on Friday, r+3 = Thursday's speed

2.7(r+3) = 3(r)

3r = 2.7r+ 8.1

.3r = 8.1

r=8.1/.3 = 27 mph on Friday

27+3 = 30 mph on Thursday

she drove 81 miles each way

3(27 = 30(2.7) = 81