Question

A lane 180m long and 5m wide is to be paved with bricks of length 20cm and breadth 15cm. find the cost of bricks that are required, at the rate of ₹750 per thousand.

Answer 1

Hello,
we indicate with L length of the lane, with l breadth of the lane.
we calculate the area of ​​a lane:
A₁=L×l=180×5=900 m²
we indicate with b length of the brick , with h breadth of the brick.
we calculate the area of a brick:
A₂=b×h=20×15=300 cm²
we convert the cm² in m² (1m²=10000 cm²)
300 cm²=0,03 m²
then
A₂=0,03 m²
we calculate the required number of bricks:
n=A₁/A₂=900/0,03=30000 bricks
we calculate the total cost of  bricks:
tot=(750×30000):1000=22500

bye :-)

Answer 2

Surface area of the lane = length X width
     S₁ = 180 m * 5 m = 900 m²

Surface area of a brick = length X breadth
     S₂ = 20 cm * 15 cm 
          = 0.20 m * 0.15 m
          = 0.030 m²

Number of bricks required to pave the lane
   = Area of lane / Area of a brick
   = S₁ / S₂
   = 900 m² / 0.03 m²
   = 30, 000

Cost of bricks
  = cost of a thousand * number of thousands of bricks
  = Rs 750 * 30,000/1000
  = Rs 22, 500