Distance, speed & distance word problems

Question

a cargo ship traveling with the current traveled 180 miles in 9 hours. On its return voyage traveling against the current, it took 18 hours to travel the same distance. Find the speed of the cargo ship and the current.

Answer 1

Hello Nicole;

That is a smart question, ships don't sail by miles, they sail by knots , one knot is 6076 foot , and each mile is 5280 Foot, so we work it out like this : .

General speed law is : Speed = Speed * Time

X = 180 / 18 = 10 Miles / Hour as general speed

And converting the numbers, we find that :

(10 Miles/Hour * 5280 Ft) / 6076 = 8.68 Knot - ship's speed in the return trip

Hope this answers clears your question;

Have a good day;

Imad Fawzi

Answer 2

180 miles in 9 hours means 20 mph total.

v_ship + v_current = 20.

On the way back we traveled 180 miles in 18 hours, or 10 mph total.

Since the ship is traveling against the current, we can look at this as

v_ship - v_current = 10

What can we tell by looking at these two? If the ship's speed is 15 mph, we can add or subtract 5 mph (the speed of the current) and everything makes sense!