GMATPrepNow
At noon, Joe and a hummingbird leave point A and travel towards point B, which is 12 miles away. At the same time Sue leaves point B and travels toward point A. Joe, Sue and the hummingbird travel at constant speeds of 3 miles per hour, 4 miles per hour, and 84 miles per hour respectively. When the hummingbird reaches Sue, it immediately changes direction and heads toward Joe. When it reaches Joe, it turns around and heads toward Sue. If this process continues until Sue and Joe meet, what is the total distance traveled by the hummingbird?
A) 49 miles
B) 84 miles
C) 121 miles
D) 144 miles
E) 168 miles
The main idea here is that
all 3 travelers travel for the SAME amount of time.
So, let's first determine the time it takes for Joe and Sue to meet.
This is a
shrinking gap question.
To determine the rate at which the gap shrinks, we'll ADD the travel speeds of Joe and Sue
That is, shrink rate = (3 miles per hour) + (4 miles per hour) =
7 miles per hourAt noon, the gap between Joe and Sue is
12 miles. time = distance/speedSo, the time it takes to reduce the gap to zero =
12/
7That is, it takes
12/
7 hours until Joe and Sue meet.
During those
12/
7 hours, the hummingbird is flying at a constant speed of
84 mph
distance = (speed)(time)So, the distance traveled by the hummingbird = (
84)(
12/
7) = 144 miles
Answer: D
Cheers,
Brent