Question

How many blocks, each 25 cm long and 12 cm wide, will be required to lay a path $12.5m$ long and $4.8m$ wide?

Answer 1

Hint: We first convert the unit of measurement of blocks and the path in the same measurement unit. We find their areas. Then we divide the area of the path with the area of 1 block to find the number of blocks required to complete the work.

Complete step-by-step solution:
We use blocks, each 25 cm long and 12 cm wide to lay a path $12.5m$ long and $4.8m$ wide.
To solve the problem, we first take the same measurement unit for the blocks and dimensions of path.
We consider them all in meters. We divide the values by 100 to convert to metre from centimetre.
So, the dimensions of the blocks will be $\dfrac{25}{100}=0.25$ m long and $\dfrac{12}{100}=0.12$ m wide each.
The area of the path will be covered by the area of the blocks.
The area of the path is $12.5\times 4.8=60{{m}^{2}}$. The area of 1 block is $0.25\times 0.12=0.03{{m}^{2}}$.
Now we divide the area of the path with the area of 1 block to find the number of blocks required to complete the work.
The number will be $\dfrac{60}{0.03}=\dfrac{6000}{3}=2000$.
The required number of blocks is 2000.

Note: We also could have changed the unit after finding the area but in that case, we should have divided the area by $100\times 100=10000$ instead of 100 as area becomes two dimensional.