Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

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. Tags confusing, question, solve Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post kozhin Calculus 1 February 17th, 2013 01:56 PM HungerGames1 Probability and Statistics 3 April 2nd, 2012 06:40 AM hoyy1kolko Probability and Statistics 5 April 15th, 2011 10:22 PM hoyy1kolko Algebra 5 December 30th, 2010 08:28 PM xnarutox Algebra 5 September 11th, 2010 03:22 PM

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