Question

the cost of the paint is rs.25 per kg. of 1 kg of paint covers 15 square feet, how much will it cost to paint outside of a cube having 5 feet each side?

Answer 1

side of cube(a)=5 feet
Surface area of cube=6a²=150feet²
paint require for 15 square feet=1kg
paint require for 1 square feet =1/15
paint require for 150 square feet=1/15 x150=10kg
cost of 1kg paint =25Rs
cost of 10kg paint will be=25x10=250 Rs

Answer 2

Outside of the cube = surface area of cube = $6 a^{2}$

a =5 feet

SA of cube = $6 (5^{2}$)

=6(25)

=150 $feet^{2}$

Paint for  15 square feet = 1 kg

So paint for 150 square feet = 10 kg

Cost of 1 kg paint = Rs.25

Cost of 10 kg paint = 25 * 10 = Rs.250