IXL - Multiply two matrices (Algebra 1 practice)

Fill in the missing number.

2	3
3	0

1	3
0	1

	9
3	9

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Learn with an example

question

Fill in the missing number.

3	2
0	3

1	0
1	3

5	6
	9

key idea

To find the element in the i^th row and j^th column of the product of two matrices, multiply each element in the i^th row of the first matrix by the corresponding element in the j^th column of the second matrix. Then add the products.

solution

To remember how to multiply two matrices, first imagine the two matrices with the second matrix moved up. Imagine the product of the two matrices sitting to the right of the first matrix and below the second matrix. The product will have the same number of rows as the first matrix and the same number of columns as the second matrix.

1	0
1	3

3	2
0	3

5	6
?	9

The blank is in row 2 and column 1. Locate row 2 of the first matrix and column 1 of the second matrix.

1	0
1	3

3	2
0	3

5	6
?	9

Pair the elements of row 2 of the first matrix with column 1 of the second matrix. To find the number that belongs in the blank, take the products of these pairs, and then take the sum of the products.

0(1) + 3(1) = 3

The
number
3
belongs
in
the
blank.

1	0
1	3

3	2
0	3

5	6
3	9

This is the product of the two matrices:

3	2
0	3

1	0
1	3

5	6
3	9

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Work it out

Not feeling ready yet? These can help:

LL.1Matrix vocabulary

P.13Multiply integers

A.4Add and subtract integers

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