I love numbers! Loved maths at school until year 10 when the teacher told me differential calculus was hard and I believed her. Can’t even remember her name to curse her!  Must go back and master it though one of these days…

Miss almost 10 has developed a love of maths too. Actually I think it is more a logical problem solving thing she has happening. Last year she was in the Math Olympiad at school and out of the 30 kids in year 4-7 all solving the same problems, she came 7th. Not bad for a fourth grader!

Anyway, she came home from school with this way cool multiplying by 11s trick and we evolved it further today!

So, for instance 35 x 11…

Basically to multiply by 11 you take the number you are multiplying (35)and split it…

3    5

The middle number of the solution is  the sum of the 2 numbers so in this case 3+5.

So the answer is 385.

But what about 3 digit numbers I hear you say!

Piece of cake!

231 x 11…

2       1

But what goes in the middle? Well you add the first 2 numbers together for the first number…

25   1

Then the next 2 numbers together…

So the answer is 2541.

Now with some twitter help we worked out how to solve when the sum of the numbers is greater than 10…

So, for instance,  96 x 11…

Now you still put the 9 and the 6 down… 9      6

But then you add them together (15) and you have to work out what to do…

Basically you put the 5 in the middle and add the 1 to the first number. So the answer is 1056.

658 x 11 is a little trickier…

6      8

Now we add the 6 and 5 and we have 11 which translates to 71    8.

Then we add the 5 and 8 (13) and again add the 10 to the previous number.

So we get 7238.

I love numbers!

Tags: 11s, Maths, multiplication

This entry was posted on Saturday, February 16th, 2008 at 6:35 pm and is filed under Imogen, Maths. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.