Two mountain bikers take off from the same place at the same time. One travels north at 4 mph, and the other travels east at 3 mph. How far apart are they after 4 hours?

A. 14 miles

B. 20 miles

C. 28 miles

D. 5 miles

20 miles (Answer B)

Step-by-step explanation:

The northbound biker travels (4 mph) (4 hr) = 16 mi, and

the eastbound biker travels (3 mph) (4 hr) = 12 mi.

They travel at right angles to one another. Thus, the Pythagorean Theorem applies here. The distance between the two bikers is d = √ ([12 mi]^2 + [16 mi]^2), or √ (144 + 256) mi, or √400 mi, which works out to 20 miles.

Answer B is correct.