Grade 11 · Math · Algebra 2

11th grade Multiply matrices, simplify matrix expressions and solve A + X = B worksheet

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Multiply matrices, simplify matrix expressions and solve A + X = B

Grade 11 Math Worksheet - Building Confidence

NameDate

Circle the best answer, or write your answer on the line.

1.
Milo has matrix A, which is 2 × 3, and matrix B, which is 3 × 4. What size is AB?
- 2 × 4
- 4 × 2
- Undefined: A and B are different sizes
- 3 × 3
2.
Ren is asked for AB, where A is 2 × 3 and B is 2 × 3. What size is AB?
- Undefined: A has 3 columns but B has 2 rows
- 3 × 2
- 2 × 3
3.
A is a 3 × 4 matrix and B is a 3 × 2 matrix. What size is AB, the product Tala wants?
- 3 × 2
- 4 × 3
- Undefined: A has 4 columns but B has 3 rows
Read this first
Matrix A
Row 1: -3, -5, -5; row 2: 3, 4, -4. Matrix B: row 1: 3, -1, 4; row 2: -3, -5, -1; row 3: 2, 2, 5. Colored: row 1 of A, (-3, -5, -5), and column 2 of B, (-1, -5, 2).
To find one entry of AB, Esme uses row 1 of A and column 2 of B. What is that entry?
Row 1: -4, -5; row 2: -3, -3. Matrix B: row 1: 3, -1; row 2: -3, 3. Luz multiplies matrices A and B. What is the entry in row 1, column 2 of AB?
Row 1: -3, 5; row 2: 4, -2. Matrix B: row 1: 2, 2; row 2: -3, 1. Milo finds one entry of the product AB. What is the entry in row 2, column 1?
Row 1: -3, 3; row 2: 1, 5. Matrix B: row 1: 6, 5; row 2: -2, 5. Pia checks row 1, column 1 of AB. What is that entry?
Row 1: -8, -8; row 2: 1, -5. Matrix B: row 1: 6, 7; row 2: -7, 8. Jun solves the matrix equation A + X = B. What is the entry in row 1, column 2 of X?
Row 1: 9, 5; row 2: -7, -7. Matrix B: row 1: 1, 2; row 2: 11, -8. Kira needs the matrix X with A + X = B. What is the entry in row 2, column 1 of X?
Row 1: 3, -4; row 2: -3, 6. Matrix B: row 1: 1, 9; row 2: 12, 1. In Luz's puzzle, A + X = B. What number goes in row 2, column 2 of X?

11th grade Multiply matrices, simplify matrix expressions and solve A + X = B worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

Multiplying matrices, matrix expressions, and solving A + X = B. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can say whether AB is defined and what size it is.
I can find any entry of AB by multiplying a row of A by a column of B.
I can solve A + X = B and kX = B, and I know that AB and BA are usually different.

Standard: N-VM.C.8 (+), N-VM.C.9 (+)

Words to know

product AB: The matrix whose entries are rows of A times columns of B.

row against a column: Multiply the pairs in order, then add the products.

inner numbers: In 2 × 3 by 3 × 4, the two 3s; they must match.

outer numbers: In 2 × 3 by 3 × 4, the 2 and the 4: the size of AB.

matrix equation: An equation like A + X = B, where X is a matrix.

Common mistakes

Gave the two middle numbers of the sizes as the size of the product.

Wrote the size of the product with columns first.

Multiplied two matrices whose sizes do not fit.

What to say

Ask: which numbers must match, and which give the size?

Ask: how many rows does AB have, from A?

Ask: is a row of A as long as a column of B?

Questions parents ask

What is the most common mistake with multiply matrices, simplify matrix expressions and solve a + x = b?

Gave the two middle numbers of the sizes as the size of the product.

How can I help my child with multiply matrices, simplify matrix expressions and solve a + x = b?

Ask: which numbers must match, and which give the size?

Are these 11th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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