Finding the Easy Way!

As mathematicians - YES we all are, we are always looking for patterns and easy ways to solve problems.  The Porritt Maths Blasters know that mathematicians like tidy numbers eg: 10, 20, 50, 100 etc.. and we are just a little bit lazy because we like solve problems quickly and easily.   This all comes down to strategy and number knowledge.

Today we were working on a multiplication problem:
If we have four boxes of chocolate and each box has 24 bars of chocolate inside, how many bars do we have altogether?

1. What is the maths? 4 x 24 (we say 4 groups of  instead of 4 times because it makes more sense to us and we can image (picture) in our heads what that looks like)
2. The next step most of us took was to simplify our problem by breaking 24 into 20 and 4 and multiplying each by 4 so 4 x 20 = 40 (we used 4 x 2 and then multiplied by 10)  and  4 x 4 = 16 (some of us knew the multiplication fact and some used doubling ie: 4 + 4 doubled)
3. Then we added together the answers to 4 x 20 = 80 and 4 x 4 = 16 to get the total 96.  The fancy name for this process is called place value partitioning.
4. Then we put the maths back into the problem and completed the problem by saying: There are 96 bars of chocolate altogether.

Then one clever cookie maths blaster said:

• "Hey 24 is only one less than 25 and I know that 25 is a quarter of 100 so if I have 4 groups of 25 and that makes 100 then 4 groups of 24 must be 4 less than 100 which is 96!"

I got my clever cookie maths blaster to draw a diagram on the white board and it looked something like this:

We were all amazed at how easily and simply she solved the problem by using her knowledge of what makes up 100 as well as rounding and compensating.