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The average weight of a class is x pounds. When a new stud

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Joined: 06 Mar 2017
Posts: 69
Location: India
Concentration: Operations, International Business
GMAT 1: 640 Q48 V31
GPA: 3.9
Re: The average weight of a class is x pounds. When a new stud  [#permalink]

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New post 01 Jul 2017, 09:30
chetan2u wrote:
PrakharGMAT wrote:
Hi Experts

Please have a look on my approach. I have created 3 equations-

1) (Sum) / N = X

2) When a new student of weight 80 is added the equations become
(Sum +80)/ (N+1) = X-1

3) When the students gain weight by 110. In this case the students have put on more weight so we just need to add 110 in the sum.
(Sum + 110) / N= X+4

After solving these equations I am getting X=102 which is not correct.
I know, I am missing something.

Can you please assist.

Thanks and Regards,
Prakhar


hi,
i find the approach to be OK BUT the highlighted portion has to be N+1 and not N..
Try putting that and check your answer



I made these 2 equations as well with N+1 as said by chetan2u, but was not able to get the value of 'x'.
Please show the solution here.
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Joined: 16 Oct 2010
Posts: 8284
Location: Pune, India
Re: The average weight of a class is x pounds. When a new stud  [#permalink]

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New post 01 Jul 2017, 22:27
3
siddreal wrote:
chetan2u wrote:
PrakharGMAT wrote:
Hi Experts

Please have a look on my approach. I have created 3 equations-

1) (Sum) / N = X

2) When a new student of weight 80 is added the equations become
(Sum +80)/ (N+1) = X-1

3) When the students gain weight by 110. In this case the students have put on more weight so we just need to add 110 in the sum.
(Sum + 110) / N= X+4

After solving these equations I am getting X=102 which is not correct.
I know, I am missing something.

Can you please assist.

Thanks and Regards,
Prakhar


hi,
i find the approach to be OK BUT the highlighted portion has to be N+1 and not N..
Try putting that and check your answer



I made these 2 equations as well with N+1 as said by chetan2u, but was not able to get the value of 'x'.
Please show the solution here.


Sum/N = X
Sum = NX

(Sum +80)/ (N+1) = X-1
(Sum + 80) = (N+1)*(X - 1)
NX + 80 = NX - N + X - 1
X - N = 81 ........ (i)

(Sum + 110) / (N+1) = X+4
Sum + 110 = (X + 4)(N + 1)
NX+ 110 = NX + 4N + X + 4
4N + X = 106 ......... (ii)


Solve (i) and (ii)
4X - 4N = 324
4N + X = 106

5X = 430
X = 86
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Re: The average weight of a class is x pounds. When a new stud  [#permalink]

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New post 19 Aug 2018, 08:37
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Re: The average weight of a class is x pounds. When a new stud &nbs [#permalink] 19 Aug 2018, 08:37

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