Question

A cheetah can run up to 70 mph. how long will it take to catch a antelope running 45 mph, if the antelope has a 50 yard head start?

Answer 1

As 1mile = 1760 yards
* represents multiplication. 

Cheetah speed = 70mph = (70 * 1760) / 3600 = 34.22 yards per seconds
Distance covered by cheetah = 34.22 * t ------------------- (1)

Now
Antelope speed = 45mph = (45 * 1760) / 3600 =  22 yards per seconds
Distance covered by antelope = 22 * t + 50--------------------- (2)
equating both equation (1) and (2);
34.22 * t = 22 * t + 50
12.22 * t = 50
t = 4.091 seconds
Hence the cheetah will catch the antelope after 4.091 seconds