The Answer

Shiloh Confederate Line Pushes Forward

Here it comes – – drum roll — the answer to the brain teaser.

Bill is 52 and Bob is 39. 

Now, I will restate the brain teaser and show you how to calculate the answer – 2 different ways.

Bill and Bob have a combined age of 91.  Bill is now twice as old as Bob was when Bill was as old as Bob is now.  How old is Bill and Bob?

The timeline below illustrates what we are talking about.  I am labeling 3 points. 

A = Bill’s Current Age; B = Bob’s Current Age; C = Bob’s Age when Bill was B years old

t  ————–C—————-B—————-A————–>

Method 1

B + A = 91

A =  2 x (B – (A – B))

A = 2 x (B – A + B)

A = 2 x (2B – A)

A = 4B- 2A

3A = 4B

A = 4/3 B

B + 4/3 B = 91

7/3 B = 91

1/3 B = 91/7 = 13

B = 13 x 3 = 39  If B = 39 then A is 52

Method 2

A = 2 x C

B = 1 1/2 x C

B + A = 91

1 1/2 C + 2C = 91

3 1/2 C = 91

(7/2)x2 C = 91 x 2

7C = 182

C = 182 / 7 = 26

If C = 26 then A = 52 and B = 39

Clear as mud?  Well, thanks for sticking it out.

If you have an old-time riddle to share, please do not be shy.  It does not need to be something quiet like this brain teaser.  It can be something people 150 years ago would have shared…

Thanks!

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