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# Ten years ago, the average age of a couple was 27 years old. Today

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Manager
Joined: 29 Nov 2018
Posts: 62
Concentration: Marketing, Strategy
Ten years ago, the average age of a couple was 27 years old. Today  [#permalink]

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07 Jan 2019, 10:06
00:00

Difficulty:

25% (medium)

Question Stats:

81% (01:13) correct 19% (02:09) wrong based on 42 sessions

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Ten years ago, the average age of a couple was 27 years old. Today also the average age of the couple and their baby is 27 years old. Find the present age of the baby.

A 4
B 3
C 2
D 5
E 7
Manager
Joined: 09 Mar 2018
Posts: 196
Location: India
Ten years ago, the average age of a couple was 27 years old. Today  [#permalink]

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07 Jan 2019, 10:30
cfc198 wrote:
Ten years ago, the average age of a couple was 27 years old. Today also the average age of the couple and their baby is 27 years old. Find the present age of the baby.

A 4
B 3
C 2
D 5
E 7

Couple's age = x+y, Baby's age = z

Ten years Ago,
$$\frac{x+y}{2}$$- 10 =27
x+y-20 = 54
x+y =74

$$\frac{x+y+z}{3}$$ =27
x+y+z = 81
z = 7

Correct Answer E
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Intern
Joined: 25 Dec 2018
Posts: 15
Re: Ten years ago, the average age of a couple was 27 years old. Today  [#permalink]

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09 Jan 2019, 01:02
cfc198 wrote:
Ten years ago, the average age of a couple was 27 years old. Today also the average age of the couple and their baby is 27 years old. Find the present age of the baby.

A 4
B 3
C 2
D 5
E 7

Couple's age = x+y, Baby's age = z

Ten years Ago,
x+y =27 * 2
x+y= 54

after 10 years

(x+10)+(y+10)+z =27 * 3
x+y+z = 81
z = 7

Correct Answer E
Manager
Joined: 18 Oct 2018
Posts: 51
Location: India
Concentration: Finance, International Business
GPA: 4
WE: Business Development (Retail Banking)
Re: Ten years ago, the average age of a couple was 27 years old. Today  [#permalink]

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09 Jan 2019, 10:44
Sum of age of parents,10 years ago= 27*2=54
Therefore, some of age of parents today= 54+10+10 =74 (adding 10 years to the age of both of the parent)
But today, age of parents and child average to 27 years.
So, sum of the ages of the three,today=27*3=81
Thus, age of child= age of all three-age of parents= 81-74=7

Hence, E
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Joined: 16 Oct 2010
Posts: 8790
Location: Pune, India
Re: Ten years ago, the average age of a couple was 27 years old. Today  [#permalink]

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09 Jan 2019, 21:20
cfc198 wrote:
Ten years ago, the average age of a couple was 27 years old. Today also the average age of the couple and their baby is 27 years old. Find the present age of the baby.

A 4
B 3
C 2
D 5
E 7

Use the concept of deviation to solve it in seconds.

Th average age of two people was 27 so they were effectively 27 years old each.
After 10 yrs, there was an extra 20 yrs deviation but average remained same so there must have been a shortfall of 20 too. The shortfall would come from the child's age so the child must be 27 - 20 = 7 years old.

Answer (E)

To learn more about this concept, check out our blog: https://www.veritasprep.com/blog/2012/0 ... eviations/
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Re: Ten years ago, the average age of a couple was 27 years old. Today &nbs [#permalink] 09 Jan 2019, 21:20
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# Ten years ago, the average age of a couple was 27 years old. Today

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