[Dr. Sivana]

Q1- Distance, Time, and Speed An old car has to travel a 2-mile route, uphill and down. Because it is so old, the car can climb the first mile—the ascent—no faster than an average speed of 15 mi/h. How fast does the car have to travel the second mile—on the descent it can go faster, of course—to achieve an average speed of 30 mi/h for the trip?

I'm only in the 140s (U.S> scale), but it didn't take me long to figure this one out.

The problem is lends itself to easy calculation because it uses numbers that divide easily into 60.

The whole trip is two miles (one mile up and down). At 30 mph, we know that is one mile every two minutes. That means the trip has to be completed in 4 minutes. But at 15 mph, the car takes 4 minutes to make the climb, meaning the return trip has to be instantaneous to make the 30 mph mark.

[Joan Kerrey]

meaning the return trip has to be instantaneous

I got the same answer but now I’m stumped on how I can achieve instantaneous, I’m still working on it. The car is still at the top of the hill.

[UCANSEE2]

That means the trip has to be completed in 4 minutes.

And just where does it state that the trip has to be completed in four minutes?

[Hot Tabasco]

You may think you're smart but you missed the key:

no faster than an average speed of 15 mi/h

Because it is so old, the car can climb the first mile—the ascent—no faster than the average speed of 15 mph

The car "CAN" travel no faster than 15 mph but did it actually do it?

AND it does not state how long it took to traverse the first uphill mile, YOU merely assumed it.........

NO MENSA FOR YOU!

[Hot Tabasco]

The answer to the question is that it is not possible. See Page 2, problem 4