How many miles did the cruise ship travel from its port to the island?

Question

Mr. and Mrs. Berg went on a cruise to a tropical island. They spent a total of 21 hours on the cruise
ship traveling to and from the island. On Friday the cruise ship left its port and traveled at an average
speed of 16 miles per hour to the island. On the return trip, the ship traveled by the same route at an
average speed of 12 miles per hour. How many miles did the cruise ship travel from its port to the
island?
[A] 294 mi [B] 108 mi [C] 144 mi [D] 56 mi

Answer 1

Hi William,

 

Let x be the time it took the ship to travel from the port to the island. Then, the time it takes for it to return to the port is 21-x.

We know that the distance between the island and port is the same. We are also given the speeds. Then, we can make use of the relationship  distance = speed*time

16x = 12*(21-x)

16x = 252 - 12x

28x = 252

x = 9 hours this is the time it took for the ship to travel to the island

Its speed was 16 mph on the way there, so

the distance between the port and the island is 

d = 16*9

= 144  miles  Choice C.