Question: 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?

1. 3
2. 7
3. 15
4. 21
5. 25

Answer:

Solution with Explanation:
Approach Solution (1):

Jacob = x years
Michael = x + 12 years
From 9 years from now, the equations will become:
2 (x + 9) = x + 21
2x + 18 = x + 21
2x – x = 21 – 18
x = 3

So, Age of Jacob = x years = 3 years
Age of Michael = x + 12 years = 3 + 12 = 15 years
After 4 years:
Age of Jacob = x + 4 = 3 + 4 = 7 years
Age of Michael = x + 12 + 4 = 3 + 12 + 4 = 19 years

Correct Option: B

Approach Solution (2):

After understanding the above situation, the equations will become like:

J = M – 12
Or
J – M = -12 --- (1)
9 years from now
(J + 9) * 2 = M + 9
2J + 18 = M + 9
2J – M = 9 – 18 = -9
2J – M = -9 --- (2)

Subtracting (1) from (2), we have:
J = 3
This is Jacob’s age today
So after 4 years:
Age of Jacob = J + 4 = 3 + 4 = 7 years

Correct Option: B

Approach Solution (3):

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 (1) and (2), we will get:
j = 3
Substitute the value in (1), you will get: m = 15
So age of Jacob in four years = 3 + 4 = 7 years

Correct Option: B

“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?”- is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book “GMAT Official Guide Quantitative Review”. To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. The GMAT Quant topic in the problem-solving part requires calculative mathematical problems that should be solved with proper mathematical knowledge.

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