Joel sailed for 3 hours at a speed of 20 miles per hour, then for 6 hours at 30 miles per hour and finally, 1 more hour at 40 miles per hour. What was the average speed of Joel during the whole sail?
.
Options:
(A) 25
(B) 27.5
(C) 28
(D) 30
(E) 32 OK. Let's think. Some random thoughts first:
3 hours at a speed of 20 miles per hour gives us Distance = 20*3 = 60 miles
6 hours at a speed of 30 miles per hour gives us Distance = 30*6 = 180 miles
1 more hour at 40 miles per hour gives us Distance = 40*1 = 40 miles
Total Distance = 60+180+40 = 280 miles
Total Time = 3+6+1 = 10 Hours
Average Speed = 280 / 10 = 28 Miles per hour The answer: (C).