Question 1004142: Going to the lake, has a mean speed of 12 mph. On the return trip the mean speed is 10 mph,. If the round trip takes 5.5 hrs., how long does the return trip take?
Answer by addingup(3677)   (Show Source):
You can put this solution on YOUR website! The formula for distance is:
d= r*t where r is the rate (another word for speed) and t is time. Since we want to find t, let's divide both sides by rate:
t= d/r
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We have two speeds, so we have to add them up:
d/r+d/r= t Let's plug in the numbers in the problem:
d/12+d/10= 5.5 Now let's find a common denominator for 12 and 10: 12, 24, 36, 48, 60. Eureka!, 60 is divisible by 12 and by 10. Multiply all sides by 60:
60/12+60/10= 330 Simplify on left, divide:
60/12=5 and 60/10=6 Now we have:
5d+6d= 330
11d= 330 Divide by 11:
d= 30 This is the distance to the lake. And the return time is:
30/10= 3 hours
Proof:
30/10= 3
30/12= 2.5
Total: 3+2.5= 5.5 We have the correct answer.
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