Why would multiplying the old fashioned way from right to left cause more errors if this way of regrouping takes up more paper?
30 5 x.
600 100 20
210 35 7
Another cool strategy is to grid it out ...Study 35 x 27
As you can see, if you follow the boxes.....you can see the answer is 945!
Explain how this is done!
Whether you are adding , subtracting , multiplying or dividing it is really helpful to break apart or use the distributive property to make NICER numbers.
Take the number 38 and add 46
THink: 30 +40 and 8 + 6 Think regrouping by place value...we put the tens together first, then the ones.
70 and 14 = 84
Try a multiplying one:
36 x 125
Think (30 + 6) x (100 + 20 + 5) Now take the 30 and times it times each of the numbers after the x sign.
30 x100 = 3000
30x 20= 600
30 x 5 = 150
So far we have 3750....and it was an easy multiply.
BUT we aren't done iuntil we have done the 6 times each ...can you do that in your head. 600 +120+ 30 = 750.
Now mentally put the two together....what did you get?
A strategy is a cool way of doing math....usually strategies make life easier for people!
Did you know that the US is one of the few countries that teach children to read from left to right but do math from right to left. Many other places start math from left to right as well and don't do the carrying thing!
Double and Half Strategy.....a FAVORITE
Take a problem such as 50 x 126 Double 50 to make 100
Then change 126 to 63.....100 x 63 is =6300....how is that?
WATCH
An easy one would be 5 x 12 = 5 x 2 x 6
which is the same as 10 x 6= 60
When you double 5 to a 10 or 50 to 100 or 500 to 1000 then you are definitely saving yourself some work!
