Q) Find the number of bricks, each measuring 25 cm x 12.5 cm x 7.5 cm, required to construct a wall 24 m long, 20 m high and 0.5 m thick while the cement and sand mixture occupies 1/20th of the volume of the wall.

Ans: 

[Approach: A wall consists of bricks and sand-cement mixture. So, if we remove the mixture’s volume, we can get volume of only bricks used in the wall. Since we have dimensions of one brick, we can calculate the volume of one brick, and then So, if we can find the number of bricks.]

Step 1: Given the dimensions of 1 brick is: 25 cm x 12.5 cm x 7.5 cm

Since volume of cuboid = l x b x h

∴ the volume of one brick = (25 x 12.5 x 7.5 ) cm³

Step 2: Dimensions of the wall to be constructed = 24 m x 20 m x 0.5 m

∴ the Volume of the wall = (24 x 20 x 0.5) m 3 = 240 m³

Step 3: Given that the sand mixture will occupy 1/20 of the wall’s total volume

∴  Volume of the Sand mixture in the wall = x wall’s total volume

=  x 240  = 12 m³

Since a wall consists of bricks and sand mixture:

∴  Wall’s total volume = Volume of the bricks in the wall + Volume of the Sand mixture in the wall

∴  Volume of the bricks in the wall = Wall’s total volume – Volume of the Sand mixture in the wall

∴  Volume of the bricks in the wall = 240 – 12 = 228 m³

∴  Volume of the bricks in the wall = 228 x (100)³ cm³

(Note: We need to ensure the units are the same before we go for division)

Therefore, 97,280 bricks will be required to construct the wall.

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