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PLEASE HELP, EASY Jeff and Lucy have been asked to wash their mom’s minivan. It takes Jeff 2 hours to wash the van by himself, and it takes Lucy 1.5 hours to wash the van by herself. How long will it take Jeff and Lucy to wash the van if they work together?
 one year ago
 one year ago
PLEASE HELP, EASY Jeff and Lucy have been asked to wash their mom’s minivan. It takes Jeff 2 hours to wash the van by himself, and it takes Lucy 1.5 hours to wash the van by herself. How long will it take Jeff and Lucy to wash the van if they work together?
 one year ago
 one year ago

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CalcmathleteBest ResponseYou've already chosen the best response.2
Ok. First find how much work is done individually in one hour.
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
So, if Jeff does the work in 2 hours, how much will he get done in 1 hour?
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
Well. In 2 hours, he gets all of the work done. In 1 hour, he gets half the work done because it's half the time it takes. Does that make sense? In other words, \(\frac12\).
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
Now, in one hour, Lucy does \(\LARGE \frac{1}{1.5}\) amount of the work. If you combine it, you get this. \[\huge\frac 12 + \frac{1}{1.5} = \frac1x\]Can you solve for x here?
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
so What equation is used to solve this problem? What does each variable represent?
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
oh ok so thats the equation we use?
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
I just gave you the equation and the variable represents how long it takes for them to do it when they combine.
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
oh thanks! so whats the solution?
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
can i cross multiply to get the solution?
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
I suppose you can, but you have to in the very least get a common denominator before that. \[\frac 12 \times \frac33+ \frac{1}{1.5} \times\frac44= \frac 1x \implies \frac 36 + \frac46 = \frac1x \implies \frac{7}{6} = \frac1x\]Now you can cross multiply. 7x = 6 x = ?
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
so it would be the fraction of 6/7 ??
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
:) so thats the solution?
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
and last question, so how long does it take for BOTH of them to wash the car together?
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
That's the answer...
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
i plug in the solution and thats the time it takes for both of them...right
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
The solutions 6/7 is how long it takes to wash the car.
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
but that doesnt make sense lol
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
@apoorvk Can you double check my work here?
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
I'm pretty sure that it would take 6/7 of an hour to wash the car together though...
 one year ago

jrosesweetBest ResponseYou've already chosen the best response.0
\OHH 6/7 of an hour. ok now it makes sense. thanks for all your help :)
 one year ago

apoorvkBest ResponseYou've already chosen the best response.1
@Calcmathlete yeah you are right  well almost. :P Actually 1/2 + 1/(1.5) gives you the work that can be completed by both kids together *in an hour*  so they basically complete 6/7 of the work in an hour. Hence they will need 1/(6/7), i.e. 7/6 hours to complete the work from scratch! :]
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
Oh ok. I was always under the impressions that since \(\LARGE \frac 1x\) represents work done in an hour, the reciprocal which is x would give you the combined rate?
 one year ago

apoorvkBest ResponseYou've already chosen the best response.1
Work done in an hour is itself the rate  isn't it? ;)
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
lol...I have always been confused at this part...I'll take your word for it XD
 one year ago

apoorvkBest ResponseYou've already chosen the best response.1
No, don't take 'my' word  understand it and take your brain's word then ;)
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
Ok. \[\frac 1x = \frac 76 = \text{Work rate}\]\[\]
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
Than last question. What exactly would 6/7 be then?
 one year ago

apoorvkBest ResponseYou've already chosen the best response.1
Oh wait  itismy bad! :O I completely misread what you'd written! ಠ_ಠ You had got 1/2 + 1/1.5 = 7/6, and so ofcourse the complete the work in 6/7 hours together!! I am really sorry, am stupid. __
 one year ago

CalcmathleteBest ResponseYou've already chosen the best response.2
lol. no worries ;)
 one year ago

apoorvkBest ResponseYou've already chosen the best response.1
I thought *1/2 + 1/1.5* was 6/7  so I made that mixup. Apologies once again!
 one year ago
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