Monday, February 14, 2011

"1" Not Such a Lonely Number

     2011 is an unusual year . . . you know, 1/1/11, 1/11/11, 11/1/11, and 11/11/11.

     The year 2011 also brings an unusual algorithm; here, give it a try.  Add the age you are (will be) in 2011 to the last two digits of the year you were born.  I bet the sum is all ones.  Get some inspiration and listen to this Three Dog Night tune as you do the calculation.
     If anyone out there knows why this happens, please leave a comment.


rick ackerly said...

Thanks. This is fun. I love numbers, too.

psychlist said...

Hi Dane!

The year of birth / age "trick" is not so tricky. If you take the year of your birth, and then add your age, you will arrive at the current year.

For example, if you were born in 1980, you will be 31 this year.

1980 + 31 = 2011.

More often than not, we start with the current year and subtract one's age to get the year of birth; we don't often calculate in the other direction.

By dropping the "19" in 19xx, we simply create a case in which anything carried from the addition will leave a 1 in the hundreds place. (The 1s in the tens and ones place are for the "11" in 2011.)

Anonymous said...

Beautiful, psychlist! I will pass this on to our 4th, 5th, & 6th graders who used the problem as a morning math challenge.