matrix multiplication

• May 2nd 2007, 10:47 AM
Cubed2D
matrix multiplication
Hi, im revising for my foundations of computer science exam, looking through passed papers, and ive come across a question thats giveing me troubles.

Matrices A, B and C have sizes 2 x a, b x 3 and 3 x c respectivly. Find the conditions on a, b, c under which:

i. The matric A . B . C exists and has the size 2 x 1

to get the resulting matrix to be 2 x 1, c would have to be equal to 1 right? im just not sure what to set a and b to to get a matrix i can multiply in to 3 x 1.

i hope that makes sence, thanks for you help!
• May 2nd 2007, 10:52 AM
Plato
c=1, correct.
What happens if a=b?
• May 2nd 2007, 11:10 AM
Cubed2D
yeah, i guess thats right. would you advise me to find some numbers that work in this situation, or just simply state that a = b?
• May 2nd 2007, 12:01 PM
Plato
Quote:

Originally Posted by Cubed2D
yeah, i guess thats right. would you advise me to find some numbers that work in this situation, or just simply state that a = b?

Any positive integer works for a.
• May 3rd 2007, 05:48 AM
Cubed2D
ahh ok, that all makes sence now, thanks for you help!