Question

a classroom 8 M long, 7 M broad and 4 M high. doors and windows occupy an area of 22 m square find the cost of painting the walls at the rate of Rs 12 per square metre .

Answer 1

first of all find the area of the 4 walls... as roof and floor is not included as a wall....
=2×(l×h+b×h)
=2(8×4+7×4)
=2×4(8+7)
=8×15
=120sq. m.

now exclude the area occupied by windows and doors from the area of the four walls.
=120-22
=98sq. m.
now finding the cost of painting the four walls at the rate of Rs. 12 per sq meter.
=98×12
=1176 Rs.

Answer 2

Answer:

Given :length of the  class room=8m

breadth of the class room=7m

height of the classroom=4m

At first find the area of the 4 walls not including the floor and the roof

formula=2(L×H+b×h)

=2(8×4+4×7)

= 2x4(8+7)

= 8x15

= 120m²

now subtract the area occupied by windows and doors from the area of the four walls :

= 120-22

= 98 m²

Now find the cost for painting the four walls :

1. rate of painting for per sq meter : rupees 12
2. area(not including the windows and doors)×12
3. 98×12
4. = rupees 1176