Question

Chris travels for a certain length of time at 40 miles per hour and Donny travels for the same length of time at 60 miles per hour. what is the average speed?

Answer 1

50

Answer 2

isnt it greater than 50?

Answer 3

im not sure im not an actual tutor but i just averaged the two 40+60= 100 divided by 2= 50

Answer 4

I think that is the trick and you are not supposed to do that. Thanks though for trying!

Answer 5

Let the time at 40 mph be t
distance covered at 40 mph = 40t
distance covered at 60 mph = 60t
total distance = 40t+60t
total time = 2t

avg speed = total distance/total time
= 100t/(2t) = 50

No trick here,
had it said, Chris travels the same distance at 40, and then at 60, you would have a "trick " question.

=

Answer 6

In this case, he answer actually is 50. Consider. Average speed is total distance divided by total time.

Without loss of generality, we can assume they each drove for 1 hour. In each hour, Chris goes 40 miles, and Donny goes 60 miles. Total distance: 100 mi. Total time: 2 hours. Average speed: 50 mph.

Usually there is a "trick" involved, making some constraints that alter the answer. In this case, the problem is surprisingly uninvolved. In fact, I wonder whether it was properly posted.

Answer 7

thanks everybody!