A classroom is 7m long, 6.5m wide and 4m high. It has one door measuring 3m*1.4m and 3 windows each measuring 2m*1m. The interior walls are to be white washed. The contractor charges Rs. 7.25 per sq. m. Find the cost of white washing the interior walls of the classroom.
Answers
We are given the dimensions of :-
- Classroom : 7 m × 6.5 m × 5 m
- Door (1) : 3 m × 1.4 m × 3 m
- Windows (3) : 2 m × 1 m
First, Let us find the surface area of the four walls of the classroom.
Since the length, breadth, height of the classroom are different so it is a cuboid.
⇒ C.S.A = LH + LB + LH + LB
⇒ C.S.A = 2L (H + B)
⇒ C.S.A = 2×7 (4 + 6.5)
⇒ C.S.A = 14 × 10.5
⇒ Area of walls = 147 m²
Now, Because the windows, door won't be white washed so we have to subtract the area of the 3 windows and 1 door.
⇒ Req. Area = Area of four walls - { 3 (Area of windows) + Area of door }
⇒ Req. Area = 147 - { 3 (2 × 1) + 3 × 1.4 }
⇒ Req. Area = 147 - ( 6 + 4.2 )
⇒ Req. Area = 147 - 10.2
⇒ Req. Area = 136.8 m²
The rate of white washing per square meters is given as ₹ 7.25 , So Let us find the cost
⇒ Cost = Rate × Area
⇒ Cost = 7.25 × 136.8
⇒ Cost = ₹ 991.8
Hence, The cost of white washing the walls of the classroom is ₹ 991.8
Answer:
Area of four walls=(2h(l+b))
=(2x4(7+6.5))
=(8x13. 5)
=108m square
area of one window =3mx1. 4m
=4.2m square
area of three window =3(2mx1m)
=6m square
total area of windows =(4.2+6)m square
=10.2m square
Area for whitewashing =(108-10.2)m square
=97.8m square
cost of 1 m square white washing = 3.50rupee
cost of 97.8m square white washing=3.50x97.8
=342.3 rupees
I hope this solution is helpful for u!!!!