The bookshop of a particular school has 10 dozen chemistry books, 8 dozen physics books, 10 dozen economics books. Their selling prices are Rs. 80, Rs. 60 and Rs. 40 each respectively. Find the total amount the bookshop will receive from selling all the books using matrix algebra.

.:

Number of Chemistry books = 10 dozen books = 120 books

Number of Physics books = 8 dozen books = 96 books
Number of Economics books = 10 dozen books = 120 books

Now, [120 96 120] $\left[ {\begin{array}{cccccccccccccccccccc}{80}\\{60}\\{40}\end{array}} \right]$
= 120 × 80 + 96 × 60 + 120 × 40
= 9,600 + 5,760 + 4,800 = 20,160

Hence, total amount received = Rs. 20,160.
Assume X, Y, Z, W and P are matrices of order 2 x n,3 x k, 2 x p, n x 3 and p x k, respectively.