Question

The length of a Rectangular Blackboard is three times Its width. If the width is $1.5\mathrm{m}$, Find its area. Also, find the cost of painting the Blackboard at the rate of $\mathrm{Rs}5.50\mathrm{per}\mathrm{sqm}$.

Answer 1

Step 1. Calculate the area of the blackboard :

Since the length of a Rectangular Blackboard is three times Its width.

$$\begin{gathered} \therefore l=3w \\ \Rightarrow =3\times 1.5\left[\because w=1.5\mathrm{m}\right] \\ \Rightarrow =4.5\mathrm{m} \end{gathered}$$

$$\begin{gathered} \therefore \mathrm{Area}\mathrm{of}\mathrm{rectangular}\mathrm{blackboard}=l\times w \\ \Rightarrow =4.5\times 1.5 \\ \Rightarrow =6.75{\mathrm{m}}^2 \end{gathered}$$

Thus, the area of the blackboard is $6.75{\mathrm{m}}^2$.

Step 2. Calculate the cost of the painting.

Since the rate of the painting is $\mathrm{Rs}5.50\mathrm{per}\mathrm{sqm}$.

$\therefore$ The total cost of painting$=6.75\times 5.50=\mathrm{Rs}37.125$

Hence, the area is $6.75{\mathrm{m}}^2$ and the cost of painting is $\mathrm{Rs}.37.125$.