Question

An open tank is 3m long ,2m wide and 1 m 50cm deep. Find the amount of paint requires to paint it's inside and outside ,if 1 kg of paint covers 20square metre . (neglect the thickness of the material)

Answer 1

total surface area of tank = 2[2(lb + bh + hl) - lb]
= 2[2(3*2 + 2*1.5 + 3*1.5) - 3*2]
= 2[2(6 + 3 + 4.5) - 6] = 2[2(13.5) - 6]
= 2[27 - 6] = 42 m²
amount of paint required = 42/20 = 2.1 kg
therefore 2.1 kg paint is required

Answer 2

Given: An open tank is 3m long ,2m wide and 1 m 50cm deep.

To find : Amount of paint requires to paint it's inside and outside ,if 1 kg of paint covers 20square metre . (neglect the thickness of the material)

Surface area of a open box = length x width +2(length x height) + 2 (width x height)

As per given: length = 3m , width = 2m , height= 1m 50 cm = 1.5 m

Surface area of the given box = 3m x 2 m + 2 (3 m x 1.5 m)+ 2 (2 m x 1.5 m)

= (6+9+6) sq. m

= 21 sq. m

Since, we need to paint inside and outside, so total required surface area to paint =2 (Surface area )

= 2(21 ) sq. m

= 42 sq. m

Amount of paint required to paint 20 sq. m= 1 kg

Then, Amount of paint required to paint 1 sq. m = $\dfrac{1}{20}$ kg

Amount of paint required to paint it's inside and outside =$42\times\dfrac{1}{20}\ kg$

= 2.1 kg

Hence, the required amount of paint = 2.1 kg