Math Is Fun Forum

mathwonka

Guest

effect on mean

hi,

"A farmer keeps a record of the weekly milk yield of his herd of 7 cows over a period of 6 months. He finds that the mean yield is 24 litres. He buys another cow that he is told produces 28 litres a week. Work out the effect this has on the mean milk yield from the cows."

the answer is 24.5... why? call me stupid but i am confused on how to answer this..

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: effect on mean

Hi mathwonka;

Since his mean was 24 liters and he has 7 cows that means he has a yield of:

7 * 24 = 168 liters per week

He adds another cow so his yield is 168 + 28 = 196 liters per week.

To get his new mean tou just divide 196 by the new number of cows:

Mean = 196 / 8 = 24.5 liters per week.

Welcome to the forum!

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

mathwonka

Guest

Re: effect on mean

hi,

sorry i worked it out like a minute after i posted it but thank you for your time anyway! i cant believe i spent 10 minutes on this problem, i feel so stupid

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: effect on mean

Hi mathwonka;

i cant believe i spent 10 minutes on this problem, i feel so stupid

I wish I could remember all the times I spent 10 weeks on a problem that someone else just answered almost immediately. When you post on a forum, you are not posting to one person. You are posting to thousands. It is really hard to stump thousands of people. Point is do not feel stupid, this happens to everybody.

Begin rant:

When I finish all my milk and vegetables and I am all grown up and have my own forum, I am going to call it MathIsGruelling. Or maybe MathIsAnnoying or MathIsBelittling or MathIsDeadly. Remember math is a four letter word and should be outlawed.

End rant:

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: effect on mean

Another way:

the additional 4 litres milk per week is equally distributed on 8 cows in total

So the average increases by 0.5 litre

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