Question

The length, breadth and height of a room are 5 m, 4 m and 3 m respectively. Find the cost of white washing the walls of the room and the ceiling at the rate of Rs.7.50 per sq.m ???


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Answer 1

Given :-

The length, breadth and height of a room are 5 m, 4 m and 3 m respectively.

To Find :-

Cost of white washing the walls of the room and the ceiling at the rate of Rs.7.50 per sq.m

Solution :-

We know that

LSA = 2(l + b)h

LSA = 2(5 + 4)3

LSA = 2(9)3

LSA = 54 m²

Now

Cost = Rate × LSA

Cost = 54 × 7.5

Cost = 54 × 75/10

Cost = Rs. 405

Answer 2

Question :-

The length, breadth and height of a room are 5 m, 4 m and 3 m respectively. Find the cost of white washing the walls of the room and the ceiling at the rate of Rs.7.50 per sq.m ???

$\begin{gathered}{\underline{\underline{{{\textsf{\textbf{\purple{given: }}}}}}}}\end{gathered}$

• length of the room = 5m
• breath of the room = 4m
• height of the room = 3m

$\begin{gathered}{\underline{\underline{\maltese{{\textsf{\textbf{\purple{to find: }}}}}}}}\end{gathered}$

• white washing the walls of the room and the ceiling at the rate of Rs.7.50 per sq.m

$\begin{gathered}{\underline{\underline{\maltese{{\textsf{\textbf{\purple{formula: }}}}}}}}\end{gathered}$

• 2h (length + breath)
• length × breath

$\begin{gathered}{\underline{\underline{\maltese{{\textsf{\textbf{\purple{Solution: }}}}}}}}\end{gathered}$

area of walls of the room = lateral surface area of cuboid

$\: \: \: \: \: :\implies\sf 2h( \: l \: + \: b \: ) \\ \\ \: \: \: \: \: :\implies\sf 2 \times 3(5 + 4) \\ \\ \: \: \: \: \: :\implies\sf 6 \times 9 \\ \\ \: \: \: \: \: :\implies\sf 54sq.cm \\ \\ \bold{\red{\: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: =\: 54sq.cm}}$

area of celling = area of base of the cuboid

$\: \: \: \: \: :\implies\sf \: l \: \times \: b \: \\ \\ \: \: \: \: \: :\implies\sf 5 \times 4 \\ \\ \: \: \: \: \: :\implies\sf 20sq.cm \\ \\ \bold{\red{ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: =\: 20sq.cm}}$

area to be white washed :-

$\: \: \: \: \: \: :\implies\sf \: (54 + 20)sq.cm \\ \\ \: \: \: \: \: \: :\implies\sf 74sq.cm \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \bold{\red{ =\: 74sq.cm}}$

now according to questions cost of white washing 1sq.m = rs 7.50

therefore the total cost of white washing the walls and ceiling of room

$\: \: \: \: \: \: :\implies\sf \: 74 \times 7.50 \\ \\ \: \: \: \: \: \: :\implies\sf rs.555 \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \sf\bold{\red{=\: rs.555}}$