Math Fun

 Try This...

1. Take the 1st 3 digits of your (any) phone number (not including the area code)
2.  Multiply by 80
3. Add 1
4. Multiply by 250
5. Add the last 4 digits of your phone number
6. Add the last 4 digits of your phone number (again)
7. Subtract 250
8. Divide the answer by 2

Did you come up with your phone number?

Try this with your students! Algebra Teachers: Have them show you why it works!

Answer: You took the original number and multiplied it by 80, then added 1 and multiplied the result by 250. In essence, you have multiplied the original number by 20,000 and added 250 to it. Then you add the last 4 digits twice. So your sum at this point is the first 3 numbers times 10,000 and doubled, the last 4 digits doubled, and an extra 250. all you need to do is take out the extra 250, then halve the number. Since the first 3 digits are still multiplied by 10,000, they end up in front, and the last 4 digits are in the final 4 place values.