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So many strategies!

September 11, 2019

We are working on multiplying, and using many strategies to solve problems.

We looked at 6×8 today, which we can break into 5×8 and add that to 1×8, or also by using subtraction find 8×8 and subtract 2×8.

We can also double the 8 and halve the 6 and multiply 3×16 to get 48.

Another way is to halve both the 6 and the 8 and then multiply our resultant by 4 (by 2 twice).

We can decompose the numbers into factors and multiply them in any order.

We can write down 1+1 so many times! Actually, we made it into an array so we could keep track. The array was 6 by 8. We can divide this array up into rectangles with friendly numbers and then add up the rectangles. Here it would be 6×4 and another 6×4 each one is 24 and 24+24 is 48.

Another really neat observation was that when the numbers hat we multiply are different by 2, we can say that the answer will be one less than the middle number’s square.

E.g. since 8-6=2 we know the answer to 6×8 is 7×7-1. We tried it with smaller models, and showed how it works with a visual model.

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