Exercise · ZW-MATRIX-MULTIPLICATION-001 · ★☆☆ Basic
If \(A\) is \(2\times 3\) and \(B\) is \(3\times 4\), what is the size of \(AB\)?
Choose one option.
Show answer
- B. \(2\times 4\)
Explanation
The product has as many rows as \(A\) and as many columns as \(B\): \(2\times 4\).
Review the concept: Matrix multiplication
The product \(AB\) of two matrices \(A\) and \(B\), when \(A\) has as many columns as \(B\) has rows, is the matrix whose \((i,j)\) entry combines row \(i\) of \(A\) with column \(j\) of \(B\).
\[(AB)_{ij}=\sum_{k=1}^{n}a_{ik}b_{kj}\]
More practice problems: matrix multiplication
- ZW-MATRIX-MULTIPLICATION-002 Compute AB for A=[1 2; 3 4] and B=[0 1; 1 0].
- ZW-MATRIX-MULTIPLICATION-003 Let A be 3× 4 and B be 4× 2. Which product is defined?
- ZW-MATRIX-MULTIPLICATION-004 For A=[2 -1; 0 3] and B=[1 4; 5 2], what is the entry (AB)_21?
- ZW-MATRIX-MULTIPLICATION-005 For A=[1 1; 0 1] and B=[1 0; 1 1], compute AB-BA.
- ZW-MATRIX-MULTIPLICATION-006 If I is the 2× 2 identity and A=[3 -2; 1 5], what is AI?
- ZW-MATRIX-MULTIPLICATION-007 Compute Amathbf v for A=[1 2 0; 0 1 -1] and mathbf v=[2; 1; 3].
- ZW-MATRIX-MULTIPLICATION-008 Which of these equalities holds for matrices A,B,C whose products are defined?
- ZW-MATRIX-MULTIPLICATION-009 Compute A^2 for A=[1 1; 1 0].