2010 February | Computer Science Schools

Archive for February, 2010

3 Math Riddles to Amaze Your Friends

Thursday, February 11th, 2010

riddle Numbers can be deceiving and manipulated in some pretty amazing ways if the observer is not paying attention. I really enjoy these types of challenges and tricks and thought that I would share some of my favorite math sequences that seem to produce amazing results with you. In reality the results are not that amazing if you pick apart the algorithm being utilized. See if you can find the hidden algortims.

Riddle 1 – The answer will reveal your age

Grab a calculator (You won’t be able to do this one in your head)
How many times do you eat your dinner in a restaurant in a week?
Multiply by 2
Add 5
Multiply by 50
If you have had your birthday this year add 1757, if you have not then add 1756
Add the current 4-digit year (2010, 2011, etc.)
Subtract 2007
Subtract the 4-digit year you were born

If you eat dinner in a restaurant at least once per week then the your age will be the last 2 digits of the result (you will get a 3-digit answer and the last 2 digits are your age).

If you do not eat dinner in a restaurant every week then the result will be your age.

Riddle 2 – The answer will reveal your phone number

NOTE: This next one is only known to work for U.S. phone numbers.

Grab a calculator (You won’t be able to do this one in your head)
Key in the first three digits of your phone number (NOT the area code)
Multiply by 80
Add 1
Multiply by 250
Add the last 4 digits of your phone number
Add the last 4 digits of your phone number again
Subtract 250
Divide number by 2

Do you recognize the answer (it should be your phone number without the area code)?

Riddle 3 – The answer will again reveal your age and number of children

Grab a calculator (You won’t be able to do this one in your head)
Enter your current age into the calculator
Multiply by 2
Add 5
Multiply by 50
Subtract 365
Add the number of children you have (0 if you have no kids)
Add 115

The first two digits of the result should be your age and the last two digits should be the number of kids you have.

You never know when little riddles like this could come in handy. You could use it to astound and amaze your children or friends. You may want to just whip these out at parties or social gatherings (now, before you laugh this IS a computer science site). If you are like me and just like breaking down riddles and algorithms then you can just add these to your own list and tweak them a little to make them your own. You could for instance change the last one to instead of how many children you have, how many beers did you drink tonight, etc. Have fun!

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