Ying Zyiyu covered the first 300 miles of a trip going at 60 mph and the last hundred going at 40 mph. What was his average speed for the entire trip?

Question

PleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePleasePlease

Answer 1

There are 300 miles covered at 60mph and 100 miles at 40mph. Split the 300 into segments of 100 miles.

Average = sum of values / number of values

average = (60 + 60 + 60 + 40) / 4

average = 220 / 4 = 55

The average speed for the total trip is 55 mph.

Answer 2

OK so let's split this problem up in to 2.

First trip: 300 miles at 60 mph.

Let's work out how long that took using:

Time (Hours) = Distance (Miles) / Speed (Miles per Hour)

That means Zyiyu was travelling for 300 miles / 60 mph = 5 hours

Second Trip: 100 miles at 40 mph

That means Zyiyu was travelling for 100 miles / 40 mph = 2.5 hours

So in the 2 trips the total distance travelled is 300 miles + 100 miles = 400 miles

The time it took to travel 400 miles is 5 hours + 2.5 hours = 7.5 hours.

Average Speed (Miles per hour) = Total Distance (miles) / Total Time (Hours)

Average speed = 400 miles / 7.5 miles = 53.33 miles per hour