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# The average age of 8 members of a group is 40 years. The age

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VP
Joined: 18 Dec 2017
Posts: 1136
Location: United States (KS)
GMAT 1: 600 Q46 V27
The average age of 8 members of a group is 40 years. The age  [#permalink]

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29 Jan 2020, 08:47
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25% (medium)

Question Stats:

78% (01:29) correct 22% (01:56) wrong based on 32 sessions

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The average age of 8 members of a group is 40 years. The age of 1 member is 55 yrs. After his retirement a new member comes in his place, whose age is 39. The average age of group will decrease by?
(a) 2
(b) 0
(c) 3
(d) 5
(e) 4.5

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Senior Manager
Joined: 16 Feb 2015
Posts: 355
Location: United States
Re: The average age of 8 members of a group is 40 years. The age  [#permalink]

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29 Jan 2020, 19:19
TheNightKing wrote:
The average age of 8 members of a group is 40 years. The age of 1 member is 55 yrs. After his retirement a new member comes in his place, whose age is 39. The average age of group will decrease by?
(a) 2
(b) 0
(c) 3
(d) 5
(e) 4.5

Explanation:
The average age is of 8 members = 40
Sum = 40x8 = 320
the total sum of 7 members age = 320-55 = 265
One new member is added in a group, So new total sum of ages = 265+39 = 304
New Average = 304/4 = 38.
So decrease in average = 40 - 38 = 2

IMO-A
Intern
Joined: 26 Jan 2020
Posts: 12
Re: The average age of 8 members of a group is 40 years. The age  [#permalink]

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29 Jan 2020, 19:40
Sum of age of 7 people = S7

1. (S7+ 55 )/ 8 = 40
2. (S7+ 39 )/8
= (S7+55)/8 - 16/8 = 40-2

So average age decreases by 2

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Re: The average age of 8 members of a group is 40 years. The age   [#permalink] 29 Jan 2020, 19:40
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