posted by .

When i have a matrix

4 X 4 and i have to multiply it by a
4 X 3
i know that the product size has to be a 4x 3

so do i do a row times column or how ?

It's easiest to learn using the notations for tensors. For any matrix X denote the entry in the i-th row and j-th column as:


Or, put differently, if you start at the top left corner and you take i steps downward and j steps to the right, you'll arrive at X_{i,j}

If X and Y are two matrices and Z = X Y, then the components of Z are given by:

Z_{i,j} = Sum over k of X_{i,k}Y_{k,j}

If X is the 4 by 4 matrix and Y is the 4 by 3 matrix, then the summation over k runs from 1 to 4, i can take values ranging from 1 to 4 and j can take values ranging from 1 to 3. Z is thus a 4 by 3 matrix.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Math (matrices)

    No one answered my matrix question. Let me rephrase: Let A, B, and 0 be 2x2 matrices. Assuming that A is invertible and 0 is all zeroes, what is the inverse of the matrix [A|0] [B|A] (that is a 4x4 matrix represented as 4 2x2 matrices) …
  2. Matrix

    How do you solve for this matrix. X*X^t=0?
  3. Algebra II

    I skipped algebra I so I never learned about matrices. If you had a 2X3 matrix & multiplied it by a 3X2 matrix, what size would the product matrix be?
  4. Advanced Math

    Find DE if matrix D= Row 1= -2,4,6 and ROW 2= 5,-7,1 and matrix E= Row 1= 1,-2 Row 2= 0,-4, and Row 3= -3,4 WORK: [(-2)(1)+(4)(0)+(6)(-3)]=-20 [(-2)(-2)+(4)(4)+(6)(4)]=44 [(5)(1)+(-7)(0)+(1)(-3)]=2 [(5)(-2)+(-7)(4)+(1)(4)]=-34 The …
  5. Math

    Fine the size of the following matrix and its additive inverse matrix. Identify if it is a square, column, or row matrix: [ 2 -3 7 1 0 4 ]
  6. Algebra 2

    Is it me or does this problem not make sense?
  7. Algebra

    Need help with these-- 40. The graph of the following system yields perpendicular lines: x + 2y = -10 -4y = 2x + 20 True or False?
  8. Java programming

    can anybody help me.. Multidimensional Array Use a two-dimensional array (for example of 3 by 3) to simulate the addition operation of two matrices. Sample output: the first matrix: 1 2 3 1 0 1 1 2 1 the second matrix: 1 1 1 2 2 2 …
  9. Precalculus

    Find the values of x and y. Matrices.. [-4 2 3 5 3 5 2 -3 1] TIMES [2 x 5] EQUALS [9 38 y] It is difficult for me to type the matrices in but.... The first matrix is 3x3 consisting of -4,2,3 in the first row.. 5,3,5 in the second row …
  10. Math

    Hi! I need help with these two questions. Thanks! :) 1.) Can we multiply the Matrix A (which is 3 x 4 matrix) by the other matrix, Matrix B (which is 3 x 4 matrix)?

More Similar Questions