1st plane flew at 600km/h

Question

15 minutes later.....
2nd plane flew at 700km/h

how long did it take the 2nd plane to overtake the 1st plane?

for my answre, I got 1.75h

Is this correct? The book said it was 1.5

Thanks

Answer 1

I got 1.75 hours for the time of the slower plane, but it asked for the time of the faster plane

15 minutes = .25 hours
so 1.75 - .25 = 1.5, the answer in your book