How much longer does it take an automobile to travel one mile at 20 miles per hour than at 30 miles per hour?

Question

a) 1 minute
b) 10 minutes
c) 20 minutes
d) None of these answers

Answer 1

20 mph ... 1/20 hr per mile

30 mph ... 1/30 hr per mile

60 minutes in an hour

Answer 2

20 mi/hr =1/3 mi/min = 3 min/mi
30 mi/hr = 2 min/mi
so, 1 minute longer

Answer 3

20mi./60min = 1/3 mi./min. = 3 min./mi.
30mi/60min. = 1/2 mi/min = 2 min/m1.
3-2 = 1 min. longer.

Answer 4

Well, 1.02 is pretty close to 1 :)