Monday, June 9, 2008

An easier way to multiply!

My friend Jenny is a teacher, and the other day she went to a math convention. They taught her a cool new way to multiply that you may want to teach your kids! Here goes:

Take any two numbers to be multiplied. half the first and double the second until you reach one. (If you get a half, say 12.5, just write 12 and keep going).
For example:
24 x 25
half is 12 50 doubled
half is 6 100 doubled
half is 3 200
half is 1.5 so write 1 400

Now cross out any that start with an even number on the left (so you cross out 24, 12, and 6.) Now add the second half of the problem (the part on the right so 200 +400) This is your answer.... 600

Here's an easier number:
8 x 7
half is 4 14
half is 2 28
half is 1 56

cross out the lines that have 8, 4, and 2.... so the answer is 56

Very cool Jenny! Thanks for sharing ...and letting me copy off your paper :)


Panamenos said...

no problem... glad it made sense. i thought it was pretty cool. my third graders always have a hard time learning the times tables for 6, 7, and 8 and I thought this might be a fun trick to teach some of them.

Shill and Company said...

This makes my head hurt. Maybe it's because it's 11:00pm, or maybe it's because I am an idiot.

Nene said...

I know for a fact it's because I'm an idiot. Me + Calculator = Best Friends!