A chocolate math problem (and solution)

Have you ever gotten an e-mail with a list of math instructions that amazingly ends up telling you your age or some other vital statistic?


Chocolate truffles at SPAGnVOLA in Gaithersburg. (Linda Davidson/THE WASHINGTON POST)

Not being much of a mathematician, I couldn’t figure out how it worked, so I asked my genius friend Lee Kraftchick, who is a Dade County assistant attorney by day but a mathematician at heart, to explain the pattern. (It’s good to have a friend who can do percentages for you.)

Below is the puzzle, and then his explanation for how it actually works.

Your Age by Chocolate Math

Work this out step by step; it should only take a minute or so. Be sure you don’t read the bottom until you’ve worked it out!

1. Pick the number of times a week that you would like to eat something chocolate — more than once but less than 10.

2. Multiply this number by 2 (just to be bold).

3. Add 5.

4. Multiply it by 50. Go ahead, use a calculator if you want.

5. If you have already had your birthday this year add 1762. If you haven’t, add 1761.

6. Now subtract the four digit year that you were born. You should have a three digit number.

Look at that number. The first digit of this was the number of times you said you wanted to eat chocolate every week.

The next two numbers are YOUR AGE!

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(bigstockphoto)

It’s actually pretty easy, according to my friend Lee.

It’s a simple math formula that winds up subtracting your birth year from the current year. It uses some numbers to distract you and make you think it is individualized because it allows you to pick the number of times that you want chocolate.

The instructions result in the following formula:

First pick a number from 1-10, call this number “a”

a times 2

plus 5

times 50

Plus 1761 if birthday has passed, 1762 if birthday has not yet occurred

minus year born

((a x 2) + 5) x 50 + 1761= 100a + 250 + 1761= 100a + 2011= 2000 +100a +11 [third digit is 100a]

subtract the third digit= 100a= 2011

2011- year you were born= your age.

Got that?

Now go eat a piece of chocolate.

Follow The Answer Sheet every day by bookmarking www.washingtonpost.com/blogs/answer-sheet .

Valerie Strauss covers education and runs The Answer Sheet blog.

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