# Math Is Fun Forum

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## #1 2006-03-10 16:35:17

Jai Ganesh
Registered: 2005-06-28
Posts: 43,630

### Average

A # 1

The average weight of three men A, B, and C is 84 kg. A fourth man D joins them and the average weight of the four becomes 80 kg. If E whose weight is 3 kg more than D replaces A, then the average weight of B, C, D, and E becomes 79 kg. Find the weight of A.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #2 2006-03-10 18:24:00

Member
Registered: 2005-11-28
Posts: 97

### Re: Average

The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
-Bertrand Russell

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## #3 2006-03-10 18:36:14

Jai Ganesh
Registered: 2005-06-28
Posts: 43,630

### Re: Average

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #4 2006-04-21 07:13:52

thinkdesigns
Member
Registered: 2005-07-21
Posts: 23

### Re: Average

Not sure but
A+B+c=252 ( average of 84*3) eq1
A+b+c+d=320 eq2
eq1 -eq2
d=68
b+c+d+e=316 eq3
e=d+3
sub into eq3
b+c+2d+3=316 eq4
eq2-eq4
A-d-3=4
a=d+7
(knowing d is 68)
a=75

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## #5 2006-04-21 16:28:34

Jai Ganesh
Registered: 2005-06-28
Posts: 43,630

### Re: Average

Well done, thinkdesigns!

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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## #6 2009-01-04 12:24:46

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

A # 2

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## #7 2009-02-06 23:39:05

JaneFairfax
Member
Registered: 2007-02-23
Posts: 6,868

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## #8 2010-04-18 19:15:38

keveenjones
Member
Registered: 2010-04-18
Posts: 2

### Re: Average

The weight of person A is 72.

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## #9 2010-04-18 19:49:38

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Average

Hi keveenjones;

Welcome to the forum!

You get 3 equations in 4 unknowns:

Clear out fractions:

Subtract 1 from 2 and you get:

D = 68. Now use that in 2 and 3:

Subtract 2 from 1

A = 75.

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.

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## #10 2010-08-16 16:18:46

jonnyj99
Member
Registered: 2010-08-16
Posts: 4

### Re: Average

There are many different types of equation for find the average. I give the easy equation are given the below.

y = f^{-1}\left(\frac{f(x_1)+f(x_2)+\cdots+f(x_n)}{n}\right),

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## #11 2010-08-16 21:18:38

Jai Ganesh
Registered: 2005-06-28
Posts: 43,630

### Re: Average

Hi jonnyj99,

The posts are understood better with LaTeX.

It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

Online

## #12 2010-08-16 21:36:14

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Average

Hi jonnyj99;

Welcome to the forum!

Ganesh is right. You forgot the math tags on both ends of your latex.

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.

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## #13 2011-02-28 17:34:15

G-man
Member
Registered: 2011-02-28
Posts: 16

### Re: Average

[hide=A's weight]85kg[hide/]

Maths!......

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## #14 2011-02-28 21:12:39

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

### Re: Average

Hi G-man;

That is close but the answer is 75, please see post #9.

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.

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