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Simple question gets a complicated answer (Posted on 2010-05-02) Difficulty: 4 of 5
Bob, when addressing my indiscreet question regarding his and his wife's ages, came up with the following answer:

"Take my age now, multiply it by my age on the wedding day, then subtract my wife's present age multiplied by her age on our wedding day.
If then you add the difference between her present age multiplied by my age on the wedding day and my present age multiplied by her wedding day age ( making no errors in your proceeding) you should end up with 511 as a result."

Since Bob knew (and rightly so) that I was ignorant about how long they were married, he assumed that either his secret will stay undisclosed forever or that I will humbly request additional data.

How wrong he was!

Without calculator, just pen and paper and 10-15 minutes of your time you will solve it too.

I bet programming is not needed.

See The Solution Submitted by Ady TZIDON    
Rating: 3.0000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
Solution Solution | Comment 2 of 5 |

x = man's age at time of wedding
y = wife's age at time of wedding
a = years from wedding until now

[x(x+a) - y(y + a)] - [x(y+a) - y(x+a)] = 511

simplified:

x² + 2a(x - y) - y²

or

(x + y + 2a)(x - y) = 511

Since 511 only has two factors - 7 & 73:

(x - y) = 7    &    (x + y + 2a) = 73

 

Since x = y + 7, substitution yields:

[(y + 7) + y + 2a] = 73   or   y + a = 33 

Since a = 33 - y, substitution in the first simplified equation yields:

x² + 2a(x - y) - y²

(y + 7)² + [2 * (33 - y) * 7] - y² = 511

Solving for y, y = 33

Thus

x = 40

y = 33

a = 0

Their current ages are 40 and 33 respectively, and they are newlyweds.


  Posted by hoodat on 2010-05-02 22:28:49
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