Algebra Motion Problems
Motion problems are based on the formula
d = rt
where d = distance, r = rate and t = time.
When solving motion problems, a sketch is often helpful and a table an be used for organizing information.
Example:
John and Philip who live 14 miles apart start at noon to walk toward each other at rates of 3 mph and 4 mph respectively. In how many hours will they meet?
Solution:
Let x = time walked.
|
r |
t |
d |
John |
3 |
x |
3x |
Philip |
4 |
x |
4x |
3x + 4x = 14
7x = 14
x = 2
They will meet in 2 hours.
Example:
In still water, Peter’s boat goes 4 times as fast as the current in the river. He takes a 15-mile trip up the river and returns in 4 hours. Find the rate of the current.
Solution:
Let x = rate of the current.
|
r |
t |
d |
down river |
4x + x |
15 / 5x |
15 |
up river |
4x - x |
15 / 3x |
15 |

The rate of the current is 2 mph.
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