SOLUTION: Two motorboats leave the dock at the same time and travel in opposite directions. One travels 9 mph faster than the other. After 2 hours the boats are 170 miles apart. How fast is

Algebra ->  Graphs -> SOLUTION: Two motorboats leave the dock at the same time and travel in opposite directions. One travels 9 mph faster than the other. After 2 hours the boats are 170 miles apart. How fast is       Log On


   

Question 1046929: Two motorboats leave the dock at the same time and travel in opposite directions. One travels 9 mph faster than the other. After 2 hours the boats are 170 miles apart. How fast is each boat traveling?
Found 3 solutions by josgarithmetic, advanced_Learner, ikleyn:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
CAR2 is faster and goes a longer distance. 
                 RATE           TIME          DISTANCE
CAR1             r               2            %28r%29%282%29
CAR2             r+9             2            %28r%2B9%29%282%29
Total                                          170

2r%2B2%28r%2B9%29=170

2r%2B2r%2B18=170

4r=170-18

4r=152

r=38

Answer by advanced_Learner(501) About Me  (Show Source):
You can put this solution on YOUR website!
2x+2(x+9)=170

Answer by ikleyn(52800) About Me  (Show Source):
You can put this solution on YOUR website!
.
Two motorboats leave the dock at the same time and travel in opposite directions. One travels 9 mph faster than the other.
After 2 hours the boats are 170 miles apart. How fast is each boat traveling?
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Let "x" be the rate (the speed) of the slower motorboat, in miles-per-hour.

Then the rate of the faster motorboat is (x+9) mph.

Then your equation is

2x + 2(x+9) = 170.

First addend in the left is the distance traveled by the slower motorboat in 2 hours.
Second addend in the left is the distance traveled by the faster motorboat in 2 hours.

Simplify and solve the equation for x:

4x + 18 = 170,

4x = 170 - 18,

4x = 152,

x = 152%2F4 = 38.

Answer. The speed of the slower motorboat is 38 mph. The speed of the faster motorboat is 38+9 = 47 mph.