Finger Calculator for 9 times multiplication.
In class we talked about ways to help us remember the nine times multiplications.
We discussed how we can check if our answer is correct by adding the numbers in our answer together to check they add up to nine.
Example:
9 x 1 = 9 (This one is easy as the answer is 9)
9 x 2 = 18 ( If we add 1 and 8 together they add up to 9)
8 x 3 = 27 ( If we add 2 and 7 together they add up to 9)
9 x 4 = 36 (If we add 3 and 6 together they add up to 9)
This helps as a checking tool.
If we multiply 9 x 5 and say the answer is 42, we can check if we are right by adding 4 and 2 together. As 2 and 4 equal 6 and not 9 we know it is wrong.
Let's try again. 9 x 5 = 45 ( 4 and 5 = 9 so we must be on the right track).
Remember this DOES NOT work for 9 x 0 = 0 as 0 x anything is always 0.
See the finger calculation tip below for another way to do 9 x multiplication.
Source: http://www.youtube.com/watch?v=C5Z8rPE1PSk&feature=player_embedded
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