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The average weight of a group of 30 friends increases by 1 kg when the

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Bunuel
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The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   13 Mar 2016, 12:40
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The average weight of a group of 30 friends increases by 1 kg when the weight of their football coach was added. If average weight of the group after including the weight of the football coach is 31 kg, what is the weight of their football coach?

A. 31 kg
B. 60 kg
C. 61 kg
D. 62 kg
E. 91 kg
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C
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gracie
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The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   13 Mar 2016, 15:17
let c=coach's weight
original total weight=(30 friends)(30 kg avge)=900kg
(900+c)/(30+1)=31 kg avge
c=61 kg
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chetan2u
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The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   13 Mar 2016, 21:23
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Bunuel wrote:
The average weight of a group of 30 friends increases by 1 kg when the weight of their football coach was added. If average weight of the group after including the weight of the football coach is 31 kg, what is the weight of their football coach?

A. 31 kg
B. 60 kg
C. 61 kg
D. 62 kg
E. 91 kg


Hi,
Again a Q which doesn't require too much of calculations..

But another approach-


Initial average= 30 and final=31..
so the weight of coach = final average and increase in weight of others= 31+30*(31-30)= 31+30=61
C

This approach is quite useful on many other Qs with cumbersome calculations or some trap
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Mathivanan Palraj
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Re: The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   13 Mar 2016, 21:44
Bunuel wrote:
The average weight of a group of 30 friends increases by 1 kg when the weight of their football coach was added. If average weight of the group after including the weight of the football coach is 31 kg, what is the weight of their football coach?

A. 31 kg
B. 60 kg
C. 61 kg
D. 62 kg
E. 91 kg

Weight of the coach is 31*31-30*30 = 61
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stonecold
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The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   18 Dec 2016, 11:19
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Here is my approach to this one ->

sum(30)=900
sum(31)=961

Hence Coach must be 61 pounds

Hence C
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Abhishek009
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Re: The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   19 Dec 2016, 11:24
Bunuel wrote:
The average weight of a group of 30 friends increases by 1 kg when the weight of their football coach was added. If average weight of the group after including the weight of the football coach is 31 kg, what is the weight of their football coach?

A. 31 kg
B. 60 kg
C. 61 kg
D. 62 kg
E. 91 kg

31*31 * 30*(31 - 1 ) = Weight of football coach

Weight of football coach = 961 - 900

So, Weight of football coach = 61

Hence correct answer will be C. 61 kg
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Re: The average weight of a group of 30 friends increases by 1 kg when the [#permalink] The average weight of a group of 30 friends increases by 1 kg when the   03 Oct 2019, 03:44
Y/30=30

(C+Y)/31=31

C+Y-Y=31^2-30^2=(31-30)(31+30)=1*61
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Re: The average weight of a group of 30 friends increases by 1 kg when the [#permalink]
03 Oct 2019, 03:44
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