Question

The cost of three mathematics books and four science books is Rs. $216$. The cost of three mathematics books is the same as that of four science books. Find the cost of each book.

Answer 1

Let the cost of a mathematics book be Rs. x and cost of a science book be Rs. y.

By given data,

$3x+4y=216$ ....... (1)

$3x=4y$ ....... (2)

The equation (2) becomes, $x=\frac{4y}{3}$ .... (3)

Substituting x in (1) we get, $3\left(\frac{4y}{3}\right)+4y=216$

$\Rightarrow 4y+4y=216\Rightarrow 8y=216$

$\therefore y=\frac{216}{8}=27$

substituting y = 27 (3) we get, $x=\frac{4\left(27\right)}{3}=36$

$\therefore$ The cost of one mathematics book = Rs. 36.

The cost of one science book = Rs. 27.