Telephone Magic

Yummy. Such a simple, yet satisfying meal. Today went well. Tomorrow is the first Game Night.

For my classes, I have a question. Do you know any good number tricks? If so, please share them. The students love them and I only have about 3. So any you know, would help! Thanks!

Here's mine. (thanks to cousin Diana!)

Telephone Magic
1. Key in the first 3 digits of your phone number (not the area code).
2. Multiply by 80.
3. Add 1.
4. Multiply by 250.
5. Plus the last 4 digits of your phone number.
6. Plus the last 4 digits of your phone number again.
7. Subtract 250.
8. Divide by 2.

See your answer? Cool huh?


Mike said...

This isn't really a trick but more of a shortcut. If you want to check whether a number is evenly divisible by 9, add up the digits of the number. If the sum of the digits is not a one digit number then sum the digits again. Keep doing it until you get a one digit answer. If the number is divisible by 9 then the one digit will always be 9. Similarly, if the once digit answer is 3,6,or 9 then the number is divisible by three.

Lets take 43812
4+3+8+1+2 = 18
1+8 = 9

43812/9 = 5368

How about 43809
4+3+8+0+9 = 24
2+4 = 6

It's divisible by three.

PS If you want to stop these annoying spam blog comments, just turn on "show word verification" in te comments setting for your blog.

Evey said...

WOW, thats a lot of spam in one post. Crazy! Anyways thanks for visiting my blog. I am super excited for hockey to be back that is why we have NHL Centre Ice so we wont miss a thing:)

hockeyfrog said...

I've been getting tons of spam lately myself.

And that number trick is pretty neat!

The Math Ninja said...

This is basically the first (and last) of my spam comments. I have seen the word verification, but had decided I didn't really need it. But this ticks me off.

Mike- Thanks for the divisibility by 9 rule. I am pretty sure there is a similar one for 11, only you add every other digit.

Big Red Lance said...

That is an awesome trick!!

I love it.