Question

Suppose that a hot air balloon moving due east at a speed of 15 mile per hour (mph) and at a constant
altitude of 100 feet passes directly overhead. Thirty seconds later, what is the distance between me and
the balloon?

Answer 1

30 seconds = 30/3600 = 1/120 hour

in 1/120 hr, balloon has gone 15/120 = 1/8 mi = 660 ft

Now you have a right triangle, with legs 100 and 660

d^2 = 100^2 + 660^2 = 445600
d = 667.5 ft