# GRE age word problem.

• Nov 21st 2009, 11:15 AM
HKarl
GRE age word problem.
This is from Barron's GRE prep guide.

If 1/2x years ago Adam was 12, and 1/2x years from now he will be 2x years old, how old will he be 3x years from now?

The solution is:

Since 1/2x years ago, Adam was 12, he is now 12 + 1/2x. So 1/2x years from now, he will be 12 + 1/2x +1/2x = 12 + x. But, we are told that at that time he will be 2x years old. So, 12 + x = 2x -----> x = 12. Thus, he is now 12 + 6 = 18, and 3x or 36 years from now he will be 18 + 36 = 54.

I highlighted the 6 in the solution above as I don't know where that comes from. Can anyone help explain the solution a bit further?
• Nov 21st 2009, 11:34 AM
Unenlightened
Quote:

Originally Posted by HKarl
This is from Barron's GRE prep guide.

If 1/2x years ago Adam was 12, and 1/2x years from now he will be 2x years old, how old will he be 3x years from now?

The solution is:

Since 1/2x years ago, Adam was 12, he is now 12 + 1/2x. So 1/2x years from now, he will be 12 + 1/2x +1/2x = 12 + x. But, we are told that at that time he will be 2x years old. So, 12 + x = 2x -----> x = 12. Thus, he is now 12 + 6 = 18, and 3x or 36 years from now he will be 18 + 36 = 54.

I highlighted the 6 in the solution above as I don't know where that comes from. Can anyone help explain the solution a bit further?

You see where the x=12 comes from?
And that he is now 12 + 1/2 x?
All it's saying here is that at the moment he is 12 + 1/2 x = 12 + 1/2 * 12 = 12 + 6 =18.
• Nov 21st 2009, 11:55 AM
HKarl
Quote:

Originally Posted by Unenlightened
You see where the x=12 comes from?

Yes

Quote:

And that he is now 12 + 1/2 x?
Yes

Quote:

All it's saying here is that at the moment he is 12 + 1/2 x = 12 + 1/2 * 12 = 12 + 6 =18.
Edit: Yes, I see it now.

Thanks.