Do you remember learning to multiply larger numbers? You probably were told to "put down the four, carry the two." (Or something like that. Room 221 mathematicians learned some new strategies.
First, we learned that we can break one large array into two smaller arrays. Therefore, we can use multiplication facts we know (or will soon know...) to solve larger multiplication problems we don't know. For example, in order to multiply 19 x6, we can make two smaller arrays: 10 x 6 and 9 x 6. (See the array above.) If we find the product of each small array, we can add them together. That gives us the total (or the product) of the larger array. So, 10 x 6 = 60 and 9 x 6 = 54. Therefore, 19 x 6 = 114.
We can also use base ten blocks to help us solve multiplication problems with larger numbers. This time, we can solve 19 x 6 by building 19 with base ten blocks 6 times. (See the base ten blocks above.) All we have to do is count up the total of base ten blocks. That helps us solve the problem 19 x 6 = 114.
Challenge your third graders to solve some multiplication problems with you!
P.S. It is crucial for children to understand that when multiplying by a multiple of 10, they need only add a zero to the product of the first digits. For example, 70 x 4 = 280. ( 7 x 4 = 28 - put a zero at the end to make 280.)
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