SOLUTION: the speed of a boat in still water is 30 mph. It takes the same time for the boat to travel 5 miles upstream as it does to travel 10 miles downstream. Find the speed of the currren

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Question 1192234: the speed of a boat in still water is 30 mph. It takes the same time for the boat to travel 5 miles upstream as it does to travel 10 miles downstream. Find the speed of the currrent
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
               SPEED             TIME         DISTANCE

UPSTRM           30-c            5/(30-c)         5

DWNSTRM          30+c           10/(30+c)        10

1%2F%2830-c%29=2%2F%2830%2Bc%29
-
2%2830-c%29=30%2Bc
60-2c=30%2Bc
3c=30
highlight%28c=10%29

Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


The other tutor showed a solution using what is probably the standard algebraic method.

Here is an alternative that I personally think is a bit easier.

The times are the same, and the downstream distance is twice the upstream distance. That means the downstream speed is twice the upstream speed.

So if c is the speed of the current, then

30+c=2(30-c)
30+c=60-2c
3c=30
c=10

ANSWER: The speed of the current is 10mph