If P, Q and R are matrices of order 2x3, 3x5 and 5x3 respectively. Then which of the following are valid?
(A) P Q R
(B) P R Q
(C) Q R
(D) R Q
(E) P R
Choose the correct answer from the options given below:
If P, Q and R are matrices of order 2x3, 3x5 and 5x3 respectively. Then which of the following are valid?
(A) P Q R
(B) P R Q
(C) Q R
(D) R Q
(E) P R
Choose the correct answer from the options given below:
Solution
Matrix P: 2×3 (2 rows, 3 columns)
Matrix Q: 3×5 (3 rows, 5 columns)
Matrix R: 5×3 (5 rows, 3 columns)
For two matrices to be multiplied, the number of columns in the first matrix must equal the number of rows in the second matrix.
If Matrix A is and Matrix B is , then is valid when , with result being .
(A) P Q R
Can P×Q be computed?
P is , Q is
Columns of P (3) = Rows of Q (3)
gives a matrix
Can (PQ)×R be computed?
is , R is
Columns of PQ (5) = Rows of R (5)
Final result: matrix
Valid
(B) P R Q
Can P×R be computed?
P is , R is
Columns of P (3) ≠ Rows of R (5)
Invalid
(C) Q R
Q is , R is
Columns of Q (5) = Rows of R (5)
Result: matrix
Valid
(D) R Q
R is , Q is
Columns of R (3) = Rows of Q (3)
Result: matrix
Valid
(E) P R
P is , R is
Columns of P (3) ≠ Rows of R (5)
Invalid
Valid expressions: (A), (C), and (D)
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