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Math Expert V
Joined: 02 Sep 2009
Posts: 58453
The average of weight of three men A,B and C is 84 kg. Another man D j  [#permalink]

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Difficulty:   45% (medium)

Question Stats: 73% (03:17) correct 27% (02:56) wrong based on 41 sessions

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The average of weight of three men A,B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man E, whose weight is 3 kg.more than that of D, replaces A, then the average weight of B,C,D and E becomes 79 kg. The weight of A is :

A. 70 kg
B. 72 kg
C. 75 kg
D. 80 kg
E. 82 kg

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Joined: 31 Oct 2013
Posts: 1464
Concentration: Accounting, Finance
GPA: 3.68
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The average of weight of three men A,B and C is 84 kg. Another man D j  [#permalink]

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Bunuel wrote:
The average of weight of three men A,B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man E, whose weight is 3 kg.more than that of D, replaces A, then the average weight of B,C,D and E becomes 79 kg. The weight of A is :

A. 70 kg
B. 72 kg
C. 75 kg
D. 80 kg
E. 82 kg

A + B + C = 84 * 3 = 252

A + B + C + D = 80 * 4 = 320

D = (A + B + C + D) - ( A + B + C) = 320 - 252 = 68.

E = D + 3 = 68 + 3 = 71.

B + C + D + E = 316.

B + C + D + 71 = 316.

B + C + D = 245.

We know,

A + B + C + D = 320

A + 245 = 320

A = 75.

C is the correct answer.
Manager  S
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Posts: 85
Location: India
GPA: 3.1
WE: Information Technology (Computer Software)
Re: The average weight of 3 men A, B and C is 84 kg. Another man D joins t  [#permalink]

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1
If E = F ( due to a typo )

we have

1. A+B+C = 84*3 = 252

2. A+B+C+D = 80*4 = 320

After A's replacement , new E = D+3

3. B+C+D+D+3 = 79*4

from 1 and 2 , D = 320 -252 = 68

from 3, B+D = 316 - (2*68+3)
= 177

So from 1 ,

A = 252 -177 = 75 Option C
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GPA: 4
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Re: The average of weight of three men A,B and C is 84 kg. Another man D j  [#permalink]

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Bunuel wrote:
The average of weight of three men A,B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man E, whose weight is 3 kg.more than that of D, replaces A, then the average weight of B,C,D and E becomes 79 kg. The weight of A is :

A. 70 kg
B. 72 kg
C. 75 kg
D. 80 kg
E. 82 kg

a+b+c= 252
and
d= 320-252 ; 68
e= 71
so
b+c= 252-a
so
252-a+68+71 = 79*4
a= 75
IMO C
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Concentration: Sustainability, Marketing
GPA: 4
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Re: The average weight of 3 men A, B and C is 84 kg. Another man D joins t  [#permalink]

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Bunuel wrote:
The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man F, whose weight is 3 kg more than that of D, replaces A then the average weight of B, C, D and E becomes 79 kg. The weight of A is:

A. 70
B. 72
C. 75
D. 79
D. 80

a+b+c=252
b+c= 252-a

now
a+b+c+d= 320
d = 68 kg and f = 71
so
252-a+68+71= 79*4
a = 75
IMO C
Target Test Prep Representative D
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Re: The average weight of 3 men A, B and C is 84 kg. Another man D joins t  [#permalink]

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Bunuel wrote:
The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man F, whose weight is 3 kg more than that of D, replaces A then the average weight of B, C, D and E becomes 79 kg. The weight of A is:

A. 70
B. 72
C. 75
D. 79
D. 80

We can create the equation:

(A + B + C)/3 = 84

A + B + C = 252

We also have:

(A + B + C + D)/4 = 80

(252 + D)/4 = 80

252 + D = 320

D = 68, and E = 68 + 3 = 71

Now we can create the equation:

(B + C + D + E)/4 = 79

B + C + 68 + 71 = 316

B + C + 139 = 316

B + C = 177

Since A + B + C = 252, subtract B + C = 177 from it, obtaining:

A = 252 - 177 = 75

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Director  V
Joined: 27 May 2012
Posts: 902
Re: The average weight of 3 men A, B and C is 84 kg. Another man D joins t  [#permalink]

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Bunuel wrote:
The average weight of 3 men A, B and C is 84 kg. Another man D joins the group and the average now becomes 80 kg. If another man F, whose weight is 3 kg more than that of D, replaces A then the average weight of B, C, D and E becomes 79 kg. The weight of A is:

A. 70
B. 72
C. 75
D. 79
D. 80

Although the answer is 75, addition of variable E is causing some confusion.I guess the last line means B C D and F.
So we have A+B+C=252
A+B+C+D=320 So D=68
Now F =71
Now we have 71+B+C+68=316 so B+C=177
A+177+68=320
so A = 320 -245 =75

P.S. Variable E seems to be in error.
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- Stne Re: The average weight of 3 men A, B and C is 84 kg. Another man D joins t   [#permalink] 17 Mar 2019, 07:11
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