3rd Grade Math Centers

Decompose a Factor

1. Solve the problems below. For each problem, show one way to find the
   product by decomposing one factor, multiplying each term, and adding the
   partial products.

a) 5 x 15 b) 24 x 3 c) 6 x 13 d) 16 x 4 e) 14 x 4 f) 7 x 13

Example: 4 x 23 =?

4 x 23 = (4 x 20) + (4 x 3) = 80 + 12 = 92

or 4 x 23 = (4 x 10) + (4 x 10) + (4 x 3) = 40 + 40 + 12 = 92

2. Create your own 1-digit x 2-digit problem. Explain how you could decompose
   a factor to quickly find the product of the two numbers mentally.

Example: 3 x 24 =?

I decompose 24 into 20 and 4. In my mind I quickly compute 3 x 20 = 60

and 3 x 4 = 12, then add 60 plus 12. The product of 3 x 24 is 72.

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