How Old is Korinth?

Date: 09/09/97 at 00:29:04
From: Ed & Roxann Phillips
Subject: Brain twister

The answer is 24.

The question is "How old is Korinth?"

The information is "Korinth is twice as old as Marin was when Korinth 
was as old as Marin is now. Marin is 18." 

How do I explain it?

Phillips et al. 

Date: 09/09/97 at 16:34:22
From: Doctor Rob
Subject: Re: Brain twister

Let Korinth's age be K. Then K - 18 is the difference in the ages 
ofKorinth and Marin.  

Then when Korinth was 18, Marin was 18 - (K - 18) = 36 - K.  
The equation you get is K = 2*(36 - K). The solution is K = 24.  

Korinth is 24 now, and Marin is 18. When Korinth was 18, Marin was 12.  
Korinth (at 24) is twice as old as Marin was (12) when Korinth was as 
old as Marin is now (18).

-Doctor Rob,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/   

Date: 09/09/97 at 22:51:06
From: Ed & Roxann Phillips
Subject: Re: Brain twister

Doctor Rob,

I don't see where you got that the difference of their ages is 18.>

Phillips et al.

Date: 09/09/97 at 18:37:10
From: Doctor Anthony
Subject: Re: Brain twister

Let k = Korinth's present age.

Let x = the number of years since Korinth was 18

Then    18+x = k   and  x years ago Marin was 18-x, so we have:

           k = 2(18-x)

Equating the two values of k we get:

      18 + x = 36 - 2x

          3x = 18

           x = 6

and finally   

           k = 18 + x  = 18 + 6 = 24

So Korinth's present age is  24 years.
       
-Doctor Anthony,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/   

Date: 09/09/97 at 23:18:41
From: Ed & Roxann Phillips
Subject: Re: Brain twister

Dr. Anthony -

Thank you very much. I can sleep again.

Phillips et al.