Question

Which can be multiplied?

Answer 1

B) BD

Explanation:

The number of columns of the first matrix (2nd dimension) must match the number of rows of the second matrix (1st dimension). When you write the dimensions together, the two middle numbers must be the same.

AB ⇒ (3x2) × (3x5) . . . . 2 ≠ 3, so cannot be multiplied

BD ⇒ (3x5) × (5x7) . . . . 5 = 5, so can be multiplied

CD ⇒ (2x3) × (5x7) . . . . 3 ≠ 5, so cannot be multiplied

DD ⇒ (3x5) × (3x5) . . . . 3 ≠ 5, so cannot be multiplied