Question

A blackboard of sides 4 m 50 cm and 3 m 20 cm is to be painted. Find the cost of painting at the rate of 25 per square metre.​

Answer 1

Answer:

The cost of painting the blackboard is Rs. 360

Step-by-step explanation:

The area of a rectangle of length $l$ and breadth $b$ is,

$Area = l\times b$

The blackboard has length,

$l=4 \ m \ 50 \ cm =4.5 m$

The breadth is,

$b=3\ m \ 20\ cm=3.2\ m$

Hence the area of the blackboard is,

$Area =l\times b=4.5\times 3.2=14.4 m^2$

The rate of painting one square meter is 25. So the cost of painting the blackboard is,

$cost = 14.4\times 25= 360$

Answer 2

Answer:

Given :-

• A blackboard of sides 4 m 50 cm and 3 m 20 cm is to be painted.

To Find :-

• What is the cost of painting at the rate of 25 per square metre.

Formula Used :-

$\clubsuit$ Area Of Rectangle Formula :

$\bigstar \: \: \sf\boxed{\bold{\pink{Area_{(Rectangle)} =\: Length \times Breadth}}}\: \: \bigstar$

Solution :-

First, we have to find the length and breadth of the blackboard :

✫ In case of length of blackboard :

$\implies \bf Length_{(Blackboard)} =\: 4\: m\: 50\: cm$

$\implies \sf Length_{(Blackboard)} =\: 4\: m + \bigg(\dfrac{50}{100}\bigg)\: m$

$\implies \sf Length_{(Blackboard)} =\: 4\: m + 0.5\: m$

$\implies \sf\bold{\blue{Length_{(Blackboard)} =\: 4.5\: m}}$

✫ In case of breadth of blackboard :

$\implies \bf Breadth_{(Blackboard)} =\: 3\: m\: 20\: cm$

$\implies \sf Breadth_{(Blackboard)} =\: 3\: m + \bigg(\dfrac{20}{100}\bigg)\: m$

$\implies \sf Breadth_{(Blackboard)} =\: 3\: m + 0.2\: m$

$\implies \sf\bold{\blue{Breadth_{(Blackboard)} =\: 3.2\: m}}$

Now, we have to find the area of blackboard :

Given :

• Length of blackboard = 4.5 m
• Breadth of blackboard = 3.2 m

According to the question by using the formula we get,

$\footnotesize \implies \sf Area_{(Blackboard)} =\: Length_{(Blackboard)} \times Breadth_{(Blackboard)}$

$\implies \sf Area_{(Blackboard)} =\: 4.5\: m \times 3.2\: m$

$\implies \sf\bold{\purple{Area_{(Blackboard)} =\: 14.4\: m^2}}$

Now, we have to find the cost of painting at the rate of 25 per square metre :

Given :

• Area of blackboard = 14.4 m²
• Rate of painting = Rs 25 per m²

Hence,

$\footnotesize \dashrightarrow \bf Cost\: of\: Painting =\: Rate\: of\: Painting \times Area_{(Blackboard)}$

$\dashrightarrow \sf Cost\: of\: Painting =\: 25 \times 14.4$

$\dashrightarrow \sf\bold{\red{Cost\: of\: Painting =\: Rs\: 360}}$

$\therefore$ The cost of painting is Rs 360 .