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anonymous
 one year ago
I will give a medal who answers this and fan them
It takes Brian 15 hours longer to build a model car than it takes John. If they work together, they can build the model car in 4 hours. Using complete sentences, explain each step in figuring out how to determine the time it would take Brian to build the car on his own
anonymous
 one year ago
I will give a medal who answers this and fan them It takes Brian 15 hours longer to build a model car than it takes John. If they work together, they can build the model car in 4 hours. Using complete sentences, explain each step in figuring out how to determine the time it would take Brian to build the car on his own

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jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1x = time it takes for Brian to build the model car on his own y = time it takes for John to build the model car on his own we're told that `It takes Brian 15 hours longer to build a model car than it takes John` so x = y+15 \[\large \frac{1}{\text{Brian's Time}}+\frac{1}{\text{John's Time}} = \frac{1}{\text{Time if they work together}}\] \[\large \frac{1}{x}+\frac{1}{y} = \frac{1}{4}\] \[\large \frac{1}{y+15}+\frac{1}{y} = \frac{1}{4}\] Do you know how to solve for y from here?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0No im so sorry this isn't my strongest subject.

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1what is the LCD of all the fractions?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1dw:1436836674900:dw

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1it's actually 4y(y+15) dw:1436836700642:dw

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1dw:1436836726938:dw

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1dw:1436836739541:dw

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1dw:1436836751079:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0First, we want to determine the rate at which both John and Brian work. Since we don't know how long it takes John to build the car, we will let x denote this time. If it takes John x hours to build the car, then we know that it takes Brian (x+15) hours to build the car because that's what the problem states. If we can set up an equation that determines x, then all we need to do is add 15 hours to it and we have Brian's time. Now, we can determine the rate at which each boy works. We can clearly see that John works at the rate of 1/x of the model car per hour and Brian works at the rate of 1/(x+15) of the model car per hour. We are told that if they work together, they can build the model car in 4 hours which means that, together, they work at the rate of 1/4 of the model car per hour. We also know that, together, they work at the rate of 1/x + 1/(x+15) of the model car per hour. Thus, our equation to solve is: 1/x + 1/(x+15)=1/4 When we solve this equation for x and add 15 hours to it, we will have solved the problem:)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Thank you guys for the help!!

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1so you see how the LCD is 4y(y+15) ?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Brian's time to build the car on his own is 20 hours

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yeah I see it now. Thank you!!

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1ok tell me what you get for y

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Wait you would distribute it right?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1did you multiply all the fractions by the LCD?

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1Multiply every fraction by the LCD 4y(y+15) to get this \[\large \frac{1}{y+15}+\frac{1}{y} = \frac{1}{4}\] \[\large {\color{red}{4y(y+15)*}}\frac{1}{y+15}+{\color{red}{4y(y+15)*}}\frac{1}{y} = {\color{red}{4y(y+15)*}}\frac{1}{4}\] \[\large 4y{\color{red}{{(y+15)}}}*\frac{1}{{\color{red}{{y+15}}}}+4{\color{red}{{y}}}(y+15)*\frac{1}{{\color{red}{{y}}}} = {\color{red}{{4}}}y(y+15)*\frac{1}{{\color{red}{{4}}}}\] \[\large 4y{\color{red}{\cancel{(y+15)}}}*\frac{1}{{\color{red}{\cancel{y+15}}}}+4{\color{red}{\cancel{y}}}(y+15)*\frac{1}{{\color{red}{\cancel{y}}}} = {\color{red}{\cancel{4}}}y(y+15)*\frac{1}{{\color{red}{\cancel{4}}}}\] \[\large 4y + 4(y+15) = y(y+15)\] notice how the denominators canceled out. From here, solve 4y + 4(y+15) = y(y+15) for y

jim_thompson5910
 one year ago
Best ResponseYou've already chosen the best response.1you're welcome
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