Question 800365
A small boat traveled upstream on a river at 10km/h and return downstream at 14km/h.
 if the round trip took 6 hours in all, how far upstream did the boat travel?
:
Let d = dist up stream (and dist downsteam)
:
Write a time equation; time = dist/speed
time up + time down = 6 hrs
{{{d/10}}} + {{{d/14}}} = 6
multiply by the least common multiple which is 70
70*{{{d/10}}} + 70*{{{d/14}}} = 70(6)
Cancel the denominators and you have:
7d + 5d = 420
12d = 420
d = 420/12
d = 35 km up the river
:
:
Confirm this solution, find the time each way
35/10 = 3.5 hrs
35/14 = 2.5 hrs
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total time: 6 hrs