Question 655559: I need help!!! 2 problems. I don't get word problems at all.
1) It takes Molly 5 minutes longer to dig a hole that it takes Holly. If they dig the hole together, it takes them 6 minuites. How long would it take Molly to dig a hole by herself? (round to nearest tenth)
2) Willie paddled 12 miles up the creek and then paddled 12 miles back. If the speed of the current was 3mph and the total trip took 4 hours, what was Willie's speed?
Thanks, Kenny klhopen@gmail.com
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! 1) It takes Molly 5 minutes longer to dig a hole that it takes Holly. If they dig the hole together, it takes them 6 minuites. How long would it take Molly to dig a hole by herself? (round to nearest tenth)
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Molly takes m minutes to dig the hole alone.
Holly takes h minutes...
"It takes Molly 5 minutes longer to dig a hole that it takes Holly" --> m = h+5
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Molly digs the hole in m minutes, so each minute she digs 1/m of the hole
Holly digs 1/h of the hole.
Together, they dig 1/m + 1/h of the hole, and it takes them 6 minutes.
--> 1/m + 1/h = 1/6
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Now it's not a "word problem."
1/m + 1/h = 1/6
m = h+5
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1/m + 1/h = 1/6
Multiply thru by 6mh to eliminate the fractions.
6h + 6m = h*m
Sub for m in the 1st equation
6h + 6(h+5) = h*(h+5)
6h + 6h+30 = h^2 + 5h
(h - 10)*(h + 3) = 0
h = -3 Ignore, they can't do it in -3 minutes.
h = 10 minutes
Holly's time alone
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m = h+5 = 15 minutes
Molly's time alone.
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That's a complex problem, don't feel bad about needing help.
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2) Willie paddled 12 miles up the creek and then paddled 12 miles back. If the speed of the current was 3mph and the total trip took 4 hours, what was Willie's speed?
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w = Willie's paddling speed
c = speed of current = 3 mi/hr
Upstream, he moved at (w-c) mi/hr
Downstream, it's (w+c) mi/hr
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d = r*t
t = d/r
t = 12/(w-3) + 12/(w+3) = 4
12/(w-3) + 12/(w+3) = 4
Can you finish that?
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