Question

"Question 4 The paint in a certain container is sufficient to paint an area equal to 9.375 m^2 . How many bricks of dimensions 22.5 cm × 10 cm × 7.5 cm can be painted out of this container?

Class 9 - Math - Surface Areas and Volumes Page 213"

Answer 1

Volume of paint = 9.375 m2 = 93750 cm2
Dimension of brick = 22.5 cm×10 cm×7.5 cm
Total surface area of a brick = 2(lb + bh + lh) cm2 
                                             = 2(22.5×10 + 10×7.5 + 22.5×7.5) cm2
                                             = 2(225 + 75 + 168.75) cm2
                                             = 2×468.75 cm2 = 937.5 cm2
Number of bricks can be painted = 93750/937.5 = 100

Answer 2

  Surface area:

Surface area of a solid object is a measure of the total area that the surface of the object occupies and it is always measured in square unit.

 

Hence surface area is also known as total surface area TSA.

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Given:

Dimension of brick = l=22.5 cm, b=10 cm, c=7.5 cm

 

Total surface area of a container= 9.375 m²

Total surface area of a brick = 2(lb + bh + lh) 

= 2(22.5×10 + 10×7.5 + 22.5×7.5) 

= 2(225 + 75 + 168.75)

= 2×468.75

 = 937.5 cm²

= 937.5/100×100 m²

Number of bricks that painted out of this container= total area painted by containers paint / total surface area of a brick

 

=9.375/ (937.5/100×100)

 =( 9.375×100×100) / 937.5

= 937500/ 9375= 100

Hence,100 bricks can be painted out.

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Hope this will help you...