If a horse runs 1.5 miles in 2 minutes and 24 seconds, what is his rate of speed in mph?

1 hour = 3600 seconds
2 minutes = 120 seconds
120 seconds + 24 seconds = 144 seconds

144/3600 = 1/25
2 minutes and 24 seconds is 1/25 of an hour.

A horse runs 1.5 miles in 1/25 of an hour.
To find how far it runs in 1 hour, set up a proportion and solve.
Let x represent the number of miles a horse can run in 1 hour.

1.5 / (1/25) = x / (25/25)
1.5 = 1/25x
1.5 (25) = 1/25x (25)
37.5 = x

37.5 miles per hour