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July 4th, 2018, 08:34 AM   #11
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You forgot the 5th line:
Quote:
 Originally Posted by skipjack Every cow was Kung Fu grazing, Those cattle were faster than lightning! In fact, it was a little bit frightening... But they mowed with expert timing! The field is now a green for putting!

July 13th, 2018, 10:20 AM   #12
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Quote:
 Originally Posted by Ganesh Ujwal 100 cows can graze a field completely in 15 days, while 60 cows can do it in 30 days. How many cows are needed to do it in 10 days? Answer is 140 cows I tried: It'd seem like it'd only take 50 cows to graze a field in 30 days if 100 can do it in 15. But in question it shows 60 cows can do it in 30 days. I am confused with this question.
That would be true if the relationship were a simple proportion. In order to solve this you have to have some notion of what kind of function there is here. Since a simple proportion does not work, the next simpler function would be linear. There exist a unique linear function that gives those two data points and that is what I would be inclined to use, but that does not give "140 cows"!

Last edited by skipjack; July 14th, 2018 at 02:06 AM.

 July 13th, 2018, 11:14 AM #13 Senior Member   Joined: Aug 2012 Posts: 2,332 Thanks: 723 Consider a spherical cow. Thanks from topsquark and JeffM1
 July 13th, 2018, 11:36 AM #14 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038
July 14th, 2018, 02:08 AM   #15
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Quote:
 Originally Posted by Country Boy That would be true if the relationship were a simple proportion.
No, it would need to be a simple inverse proportion,
i.e. (number of cows) = k/(number of days), where k is a constant.

Quote:
 Originally Posted by Country Boy Since a simple proportion does not work, the next simpler function would be linear. There exist a unique linear function that gives those two data points and that is what I would be inclined to use, but that does not give "140 cows"!
Modifying the simple inverse proportion by using

(number of cows) = k/(number of days) + p, where k and p are constants,

implies a unique solution, namely k = 1200 and p = 20.

Using those values and substituting number of days = 10,
one gets the expected answer that number of cows = 140.

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