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Explain solution for rd sharma class 12 chapter Algebra of matrices exercise 4.3 question (72) math

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Answer: The total amount the store will receive from selling all the items Rs 1597.20

Hint: Matrix multiplication is only possible, when the number of columns of first matrix is equal to the number of rows of second matrix.

Given: 10 dozen physics books, 8 dozen chemistry books and 5 dozen mathematics books. Selling price of physics books=Rs 8.30 chemistry books=Rs 3.45 and mathematics=Rs 4.50

Matrix representation of stock of various types of book in the store is given by,

\begin{array}{l} X=\left[\begin{array}{lll} 10 \times 12 & 8 \times 12 & 5 \times 12 \end{array}\right] \\\\ X=\left[\begin{array}{lll} 120 & 96 & 60 \end{array}\right] \end{array}

Matrix representation of selling price of each book is given

Y=\left[\begin{array}{l} 8.30 \\ 3.45 \\ 4.50 \end{array}\right]

So, total amount received by the store from selling all the items is given by

\\X Y=\left[\begin{array}{lll} 120 & 96 & 60 \end{array}\right]\left[\begin{array}{l} 8.30 \\ 3.45 \\ 4.50 \end{array}\right] \\\\ X Y=[(120)(8.30)+(96)(3.45)+(60)(4.50)] \\\\ X Y=[996+331.20+270] \\\\ X Y=[1597.20] \\\\

Total received amount=Rs 1597.20

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