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Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 02:16
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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 02:18



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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 02:25
Bunuel wrote: Jacob is now 12 years younger than Michael. If 9 years from now Michael will be twice as old as Jacob, how old will Jacob be in 4 years?
(A) 3 (B) 7 (C) 15 (D) 21 (E) 25
Kudos for a correct solution. Jacob=x years, Mike=x+12 years 9 years from now, 2(x+9)=x+21 2x+18=x+21 x=3 x+4=7 years Answer B



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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 03:19
Bunuel wrote: Jacob is now 12 years younger than Michael. If 9 years from now Michael will be twice as old as Jacob, how old will Jacob be in 4 years?
(A) 3 (B) 7 (C) 15 (D) 21 (E) 25
Kudos for a correct solution. J = M  12 or J  M = 12 .... (1) 9 years from now.. (J + 9)*2 = M + 9 2J + 18 = M + 9 2J  M = 9 ..... (2) Subtracting (1) from (2) J = 3 This is Jacob's age today. In 4 years, Jacob's age will be 7. Answer: (B)
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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 03:56
[quote="Bunuel"]Jacob is now 12 years younger than Michael. If 9 years from now Michael will be twice as old as Jacob, how old will Jacob be in 4 years?
(A) 3 (B) 7 (C) 15 (D) 21 (E) 25
Jacob is now 12 years younger than Michael => J=M12  Eq1
If 9 years from now Michael will be twice as old as Jacob=> 2(J+9)=M+9  Eq2
Substitute Eq1 in Eq2 to get 2(M12+9)=M+9 Sp M=15 and J=3
how old will Jacob be in 4 years ?=>J+4=3+4=7



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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 11:55
Bunuel wrote: Jacob is now 12 years younger than Michael. If 9 years from now Michael will be twice as old as Jacob, how old will Jacob be in 4 years?
(A) 3 (B) 7 (C) 15 (D) 21 (E) 25
Kudos for a correct solution. Let age of Jacob be j years and Michael be m years Present age as per given statement > j = m 12......... (1) as per second given statement > m +9 = 2 (j + 9) > m  2j = 9........(2) Solving for (1) and (2) J = 3 , substitute the value in (1) you get M = 15. SO age of jacob in four years = 3 + 4 = 7
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Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 12:02
Jacob is now 12 years younger than Michael J=M12Equation 1 9 years from now Michael will be twice as old as Jacob M= 2(J+9) Equation 2 by solving Equations 1 & 2 we get J =3after 4 years Jacob will be 3+4=7 yearsAns is B
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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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11 Sep 2015, 12:29
Jacob's present age = J Michael's present age = M
"Jacob is now 12 years younger than Michael"
J = M  12 M = J + 12 (i)
"9 years from now Michael will be twice as old as Jacob"
M + 9 = 2(J + 9)
from (i) ,
(J +12) +9 = 2J + 18 J = 21  18 = 3
"how old will Jacob be in 4 years?"
J + 4 = 3 + 4 = 7
Option B.



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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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14 Sep 2015, 06:22
Bunuel wrote: Jacob is now 12 years younger than Michael. If 9 years from now Michael will be twice as old as Jacob, how old will Jacob be in 4 years?
(A) 3 (B) 7 (C) 15 (D) 21 (E) 25
Kudos for a correct solution. KAPLAN OFFICIAL SOLUTION:The first step to answering this question is translating the information in the problem into equations. If Jacob is 12 years younger than Michael, we can say that J = M – 12, where J is Jacob’s age and M is Michael’s age. The second equation is a bit trickier to determine. You must keep in mind that it refers to the relationship between their ages in 9 years. Thus, Jacob will be J + 9 years old and Michael will be M + 9 years old. The equation we can then write if Michael will be twice as old as Jacob in 9 years is M + 9 = 2(J + 9). Because the question wants us to solve for Jacob’s age in 4 years, we should next rewrite our first equation as M = J + 12. This allows us to substitute J + 12 for M in the second equation, which becomes (J + 12) + 9 = 2(J + 9). Then solve for J as follows: J + 12 + 9 = 2(J + 9) J + 21 = 2J + 18 3 = J. However, you must remember that the question asks for Jacob’s age in 4 years. Since Jacob is 3 years old today, we know that he will be 7 years old in 4 years. Thus, the correct answer is choice (B).
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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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14 Sep 2015, 10:35
Their age gap will never change, be it 9 years later or a 100 years later. So 9 years from now, M  J = J, where J = 12. J's current age = 129 = 3. 4 years from now, he will be 7. Cheers, Sam



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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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20 Apr 2018, 03:28
M = M 1 equation J = M  12. 2 equation Then after 9 year M = M+9 J = M 12 + 9 2(M3) = M+9 2M6 = M+9 M=15....This is a Micheal age we need to find Jacob age, then put the value into second equation..you will get J=3 This is not final answer, we need to find next four year age of Jacob, so J = 3 + 4 = 7 So, J=7, this is our final answer!



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Re: Jacob is now 12 years younger than Michael. If 9 years from now Micha [#permalink]
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23 Apr 2018, 17:35
Bunuel wrote: Jacob is now 12 years younger than Michael. If 9 years from now Michael will be twice as old as Jacob, how old will Jacob be in 4 years?
(A) 3 (B) 7 (C) 15 (D) 21 (E) 25 We can let Jacob’s age today = j and Michael’s age today = m and create the equations: j = m  12 We know that 9 years from now, Michael will be (m + 9) years old, and Jacob will be (j+ 9) years old. At that time in the future, Michael will be twice Jacob’s age. Thus, we have: m + 9 = 2(j + 9) m + 9 = 2j + 18 m = 2j + 9 Substituting we have: m = 2(m  12) + 9 m = 2m  24 + 9 15 = m So j = 15  12 = 3. So, in 4 years, Jacob will be 7. Answer: B
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