Math Is Fun Forum

atut

Member

Registered: 2008-04-23

Posts: 30

A , B , C

A B and C represent three numbers. The mean of A, B and C is A. Caculate the mean of B and C.

Thanks hope u can help.;)

Ricky

Moderator

Registered: 2005-12-04

Posts: 3,791

Re: A , B , C

What does it mean to have the mean be A?  Pretty simple, it's:

Now just solve that equation for:

In other words, you want to solve that equation for B + C, then divide both sides by 2.

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"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

atut

Member

Registered: 2008-04-23

Posts: 30

Re: A , B , C

I need the answer

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: A , B , C

Use Ricky's first equation and try to find an expression for B+C in terms of just A.

Splitting the left side to get

would be a good starting point.

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Why did the vector cross the road?
It wanted to be normal.

John E. Franklin

Member

Registered: 2005-08-29

Posts: 3,588

Re: A , B , C

Think points on a ruler.
If middle is A, then A is in the middle, and B is left and C is right same distance.
There is no other way!
So easy, B average C is A too!
God I'm smart.

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igloo myrtilles fourmis

orcared

Member

Registered: 2008-07-12

Posts: 6

Re: A , B , C

Dividing both sides by 2, we have

So the mean of B and C is also A.

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