Speed distance time

Question

adult drivers 105 miles at an average speed of 70 miles per hour. he then drives 100 miles an average speed of 40 miles per hour calculate his average speed for the whole journey.

Answer 1

distance=rate*time

total distance=rate*total time

105=70*t

t=105/70

t=1.5 hours

100=40*t

t=100/40

t=2.5 hours

105+100=205 miles

1.5+2.5=4 hours

205=r*4

r=205/4

r=51.25 mile per hour is the average speed for the trip