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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
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Bunuel wrote:
If John is x years old now, and his father is 44 years old now, in how many years will John’s father be twice as old as John will be at that time?

A. 44 – 2x
B. 44 – x
C. 44
D. 2x
E. x – 22





Let n = the number of years that will pass until John’s father will be twice as old as John will be at that time. We see that John’s father will be (44 + n) and John will be (x + n); the relationship between the two ages will be that John’s father is twice as old. Thus, we have:

44 + n = 2(x + n)

44 + n = 2x + 2n

44 - 2x = n

Answer: A
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
Expert Reply

Solution



Given
In this question, we are given that
    • John is x years old now, and
    • His father is 44 years old now

To find
We need to determine
    • In how many years will John’s father be twice as old as John will be at that time

Approach and Working out
Let us say after y years John’s father age will be twice that of John’s
    • Age of John after y years = x + y
    • Age of his father = 44 + y
    • Thus, 44 + y = 2(x + y)
      o Implies, y = 44 – 2x

Thus, Option A is the correct answer.

Correct Answer: Option A
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
John's present age = x
Father age = 44

y = years from now

\(44 + y = 2(x+y)\)

\(44 + y = 2x + 2y\)

\(44 = 2x + y\)

\(44-2x = y\)

Answer is A.
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
BrentGMATPrepNow wrote:
Bunuel wrote:
If John is x years old now, and his father is 44 years old now, in how many years will John’s father be twice as old as John will be at that time?

A. 44 – 2x
B. 44 – x
C. 44
D. 2x
E. x – 22
PS21252


GIVEN:
x = John's PRESENT age
44 = the father's PRESENT age

Let k = the number of years it will take until John's father is TWICE as old as John

So....
x + k = John's age IN k YEARS
44 + k = the father's IN k YEARS

In k years, we want the father's age to be twice John's age
In other words we want: 44 + k = (2)(x + k)
Expand to get: 44 + k = 2x + 2k
Subtract k from both sides to get: 44 = 2x + k
Subtract 2x from both sides to get: 44 - 2x = k

In other words, in 44 - 2x years, the father's age will be twice John's age

Answer: A

Cheers,
Brent


Hi BrentGMATPrepNow, is calculation below correct also? Thanks Brent

x = John's PRESENT age
44 = the father's PRESENT age

F=2J
F=2x
44 = 2x
44 - 2x
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
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Top Contributor
Kimberly77 wrote:

Hi BrentGMATPrepNow, is calculation below correct also? Thanks Brent

x = John's PRESENT age
44 = the father's PRESENT age

F=2J
F=2x
44 = 2x
44 - 2x


Although your calculations are incorrect, you were able to reach the correct answer coincidentally.
We aren't told the father is PRESENTLY twice as old as his son.
However, your solution suggests that the father IS presently twice as old as his son, because you have concluded that 44 = 2x, where 44 and x are the father's and son's ages respectively.
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
Let n be the no. of years after which John’s father will be twice as old as John at that time.
44 + n = 2(x + n)
44 + n = 2x + 2n
44 - 2x = n
Answer: A.

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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
BrentGMATPrepNow wrote:
Kimberly77 wrote:

Hi BrentGMATPrepNow, is calculation below correct also? Thanks Brent

x = John's PRESENT age
44 = the father's PRESENT age

F=2J
F=2x
44 = 2x
44 - 2x


Although your calculations are incorrect, you were able to reach the correct answer coincidentally.
We aren't told the father is PRESENTLY twice as old as his son.
However, your solution suggests that the father IS presently twice as old as his son, because you have concluded that 44 = 2x, where 44 and x are the father's and son's ages respectively.


Understand now. Thanks BrentGMATPrepNow the great clarification :thumbsup: :)
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
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Re: If John is x years old now, and his father is 44 years old now, in how [#permalink]
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