SOLUTION: Lisa traveled to her cabin on the lake and back. the trip there took five hours and the trip back took 6 hours. she averaged 45 km/h on the return trip. what was her speed for the

Question 535084: Lisa traveled to her cabin on the lake and back. the trip there took five hours and the trip back took 6 hours. she averaged 45 km/h on the return trip. what was her speed for the trip there?
Found 2 solutions by josmiceli, lmeeks54:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = speed going to lake in km/hr
Let = distance to lake in km
To lake:

Trip back:

By substitution:

km/hr
Answer by lmeeks54(111) (Show Source): You can put this solution on YOUR website!
The key to problems such as this is to understand the basic formulas linking time, distance, and rate (speed). For this problem, d = distance traveled in km, t = time traveled in hrs, and r = the rate of travel in km/hr. The basic formula is: d = r * t, which could also be: t = d / r or r = d / t
...
Lisa made two trips of identical distance (a safe assumption for math problems in class, but not necessarily a safe assumption in real life since Lisa could have driven two different routes). So, we can use data and calculations from one trip to help figure out the other trip.
...
Trip 1:
d = unknown, r = unknown, t = 5 hrs
Trip 2:
d = unknown, r = 45 km/hr, t = 6 hrs
...
Trip 2, calculate for d: d = r * t = 45 km/hr * 6 hrs = 270 km
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Take this result back to Trip 1:
d = 270 km, r = unknown, t = 5 hrs; solve for r: r = d / t = 270 / 5 = 54 km/hr
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54 km/hr is the answer to problem.
...
cheers,
Lee
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