A little math quiz

Here is an interesting little math problem.

A man drives a car for one mile at 60 miles per hour and for another mile at 120 miles per hour. What is his average speed?

 

That looks to me like 60 seconds at 60 mph and 30 seconds at 120 mph. 90 seconds total travel.

Total speed = (60*(60/90))+(120*(30/90))

So 80 mph I think.

 

Or if you don't like that method:

Total travel is 2 miles in 90 seconds.
So 1 mile in 45 seconds. (divide by 2)
0.022222 miles per second. (1 / 45)
1.33333 miles per minute. ((1/45)*60)
And 80 mph. (((1/45)*60)*60)

 

Interesting how different people come up with different procedures. One of my friends said:

Car traveled 2 miles / 1.5 min (first mile took 1.0 minutes, the second took 0.5 minutes) = average speed in miles/minute. So 2/1.5 miles per min multiplied by x/60 gives miles per hour. x = 80 mph

Another friend explained it this way:

He drives 2 miles in 1.5 minutes, so his average speed is (2/1.5) x 60 = 80mph.

 

The best answer so far!!!!

I expect your van also can't accelerate from 60mph to 120mph instantaniously.