Word Problems/math

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quietchung wrote at 2009-05-10 17:23:48
here is an algebraic method



for direct proportion you generally use the formula y = kx



for inverse proportion you use y = k/x



Your question is inverse proportion as when one thing gets smaller another thing gets bigger i.e as the number of people increase the less days it will take.



we know that the number days it took in the beggining is 6 and the number of people were 4, so we want to find out how long it would take one person we can do this but substituting it into the formula 6 = k/4 (assuming you know basic algebra we times both sides by 4 to get 24 = k

and we now know that it would take one person 24days to complete the job, but we want to know how many PEOPLE it would take to complete the job in 3 days so we do this 3 = 24/x (x is the number of people), if we times both sides by x we get 3x = 24 and then divide both sides by 3 to get X the number of people x = 24/3 which is 8!



Hope that helps


Dolche wrote at 2011-04-29 14:27:38
Instead of using cross multiplication as in direct proportions, you will use direct multiplication:



4     6 days    

___ = ___

x     3  days



so it will look like this:



x = (4*6)/3

x = 24/3

x = 8



Dulce  


Qwerty wrote at 2013-01-25 05:44:29
By using the formula x1*x2=y1*y2         We get 4*6=3*x.       =24/3=8

The answer is 8men


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