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Seven years ago Bob was k times as old as Ann. If Ann is now 11 years

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Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 19 Feb 2015, 08:48
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 19 Feb 2015, 22:29
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Bunuel wrote:
Seven years ago Bob was k times as old as Ann. If Ann is now 11 years old, what is Bob’s present age in terms of k?

A. 7 + 4k
B. 11/k + 7
C. 11 - 7/k
D. 11 - k/7
E. 4k - 7


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X-7=K(Y-7)
X-7=4K
X=7+4K
Answer A
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 20 Feb 2015, 01:29
Answer = A. 7 + 4k

.................... Bob ......................... Ann


7 yrs ago ....... (b-7) .......................... 4

Current age ...... b ............................. 11 (Say current age of Bob = b)

Given that 4k = b-7

b = 4k + 7
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 20 Feb 2015, 13:11
Hi All,

Most Test Takers would approach this question using a "system" of equations, which is fine. As long as you handle the "time shift" correctly, then you'll get to the correct answer. This question can also be solved by TESTing VALUES - you just have to note that Ann was 4 years old seven years ago....

We're told that 7 years ago, Bob was K times as old as Ann. Then we're told that Ann is NOW 11 years old. Thus, seven years ago, Ann was 11-7 = 4 years old....

Seven Years Ago:
Ann = 4 years old

Let's say that K = 2
Bob = 2(4) = 8 old

Present Day:
Ann = 11 years old
Bob = 8+7 = 15 years old

The question asks for Bob's age NOW, relative to K...

Answer A: 7 + 4(2) = 15 This IS a match
Answer B: 11/2 + 7 = 12.5 NOT a match
Answer C: 11 - 7/2 = Less than 15
Answer D: 11 - 2/7 = Less than 15
Answer E: 8 - 7 = Less than 15

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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 21 Feb 2015, 09:52
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1
Firstly set up equation:

(B-7) = k (A - 7)

Now we now A is 11 in the present, therefore, A was 4 years old, 7 years ago:

(B-7) = k * 4

B = 4k + 7

Answer A
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 22 Feb 2015, 12:08
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 14 Dec 2019, 06:45
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Bunuel wrote:
Seven years ago Bob was k times as old as Ann. If Ann is now 11 years old, what is Bob’s present age in terms of k?

A. 7 + 4k
B. 11/k + 7
C. 11 - 7/k
D. 11 - k/7
E. 4k - 7


If Ann is NOW 11 years old, then 7 YEARS AGO, Ann was 4 years old.

Seven years ago Bob was k times as old as Ann.
So, 7 YEARS AGO, Bob's age was 4k

What is Bob’s present age in terms of k?
To find Bob's present age, we need to add 7 to his age 7 years ago.
So, Bob's PRESENT age = 4k + 7

Answer: A

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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 01 Jan 2020, 18:40
Bunuel wrote:
Seven years ago Bob was k times as old as Ann. If Ann is now 11 years old, what is Bob’s present age in terms of k?

A. 7 + 4k
B. 11/k + 7
C. 11 - 7/k
D. 11 - k/7
E. 4k - 7


Kudos for a correct solution.


Letting B and A equal Bob’s and Ann’s current ages, respectively, we can create the equation:

B - 7 = k(A - 7)

Since A = 11, we have:

B - 7 = k(11 - 7)

B - 7 = 4k

B = 4k + 7

Answer: A
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years  [#permalink]

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New post 02 Jan 2020, 21:00
Start with present and move backward.

11-7 = 4 --> 4k --> now add 7
A 4k +7
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Re: Seven years ago Bob was k times as old as Ann. If Ann is now 11 years   [#permalink] 02 Jan 2020, 21:00
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