It takes 2 hours for a boat to travel 28 miles downstream. the same boat can travel 18 miles upstream in 3 hours .find the rate of the stream's current.

  4 mph

Step-by-step explanation:

The speed downstream is (28 mi)/(2 h) = 14 mph.

The speed upstream is (18 mi)/(3 h) = 6 mph.

The speed of the current is half the difference of these:

  (14 mph -6 mph)/2 = 4 mph

The current adds to the downstream speed and subtracts from the upstream speed, so the difference of those speeds is twice the current's speed.

answer: the angel abc is 30°,and the abc is a triangle where the angel bac is 90°

so ac is the half of 24=12ft,and from the pythagorean theorem we find ba

ba=√bc^2-ac^2=√576-144=√432=12√3ft

so bac is 12+12√3=12(1+√3)ft