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Find the number of bricks, each measuring 24┬аcm├Ч12┬аcm├Ч8┬аcm, required to construct a wall 24┬аm long, 8┬аm high and 60┬аcm thick if 10% of the wall is filled with mortar?
45000
450000
450
4500
45000
Convert all units to centimeters first. Note that 24┬аm=2400┬аcm, 8┬аm=800┬аcm, and 60┬аcm is already in cm. Since 90% of the wall volume is occupied by bricks, compute (2400├Ч800├Ч60├Ч0.9)/(24├Ч12├Ч8).
Brick dimensions = 24┬аcm├Ч12┬аcm├Ч8┬аcm, Wall dimensions = 24┬аm├Ч8┬аm├Ч60┬аcm, Mortar volume = 10% of the wall volume
N=Volume┬аof┬аone┬аbrickVolume┬аof┬аwall├Ч(1тИТpercentage┬аof┬аmortar)тАЛ
Convert all units to centimeters first. Note that 24┬аm=2400┬аcm, 8┬аm=800┬аcm, and 60┬аcm is already in cm. Since 90% of the wall volume is occupied by bricks, compute (2400├Ч800├Ч60├Ч0.9)/(24├Ч12├Ч8).
Forgetting to subtract the 10% mortar volume from the total wall volume or mixing up meters and centimeters.
Step 1: Convert all units to centimeters
Since the brick dimensions are given in centimeters (24┬аcm├Ч12┬аcm├Ч8┬аcm), convert the wall dimensions from meters to centimeters: Length = 24┬аm=2400┬аcm, Height = 8┬аm=800┬аcm, Thickness = 60┬аcm.
Length=2400┬аcm,Height=800┬аcm,Thickness=60┬аcm
Step 2: Calculate total volume of the wall
Multiply the length, height, and thickness of the wall to find its total volume.
VwallтАЛ=2400├Ч800├Ч60=115,200,000┬аcm3
Step 3: Account for mortar volume
Since 10% of the wall is filled with mortar, the volume occupied by bricks is 90% of the total wall volume.
VbricksтАЛ=0.90├Ч115,200,000=103,680,000┬аcm3
Step 4: Calculate volume of a single brick
Find the volume of one brick using its given dimensions.
V1┬аbrickтАЛ=24├Ч12├Ч8=2304┬аcm3
Step 5: Calculate the required number of bricks
Divide the total volume occupied by bricks by the volume of one brick to find the total number of bricks.
N=2304103,680,000тАЛ=45,000
A is correct because the total effective volume of the wall occupied by bricks is 1,03,680,000┬аcm3 and dividing this by the volume of a single brick (2304┬аcm3) yields 45,000 bricks.
Similar mensuration problems frequently appear in civil engineering and architectural estimates where mortar or cavity deductions must be subtracted from structural volumes.