 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2001/paper-1/10/a/ii/solution

Apply row-column matrix multiplication twice:

(A BC)_{ij} = a_{ik} b_{k ℓ} c_{ℓ j} .

The indices

i, j

are free, while

k, ℓ

are summed.

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