Question

The number of marble slabs of size 20 cm $ \times $ 30 cm required to Pave the floor of a square room of side 3 meters is
A.100
B.150
C.225
D.25

Answer 1

Hint: The total area of the Pave floor of the square room needed to be covered with slabs. So the sum of area for n such slabs will be equal to the total surface area of pave floor. Hence we can find marble slabs.

Complete step-by-step answer:
Let’s begin with the area of the slab each of them have 20 cm $ \times $ 30 cm of size and the total area needed to be covered is square of size 3 m.
Then finally we need to convert each and everything in a single dimension as we know that 100 cm = 1m. The final Pivot is 300 cm.
1 slab covers the area of $20 \times 30 = 600{\text{c}}{{\text{m}}^2}$ and we need $300 \times 300 = 90000{\text{c}}{{\text{m}}^2}$ of area to be covered with the slabs. Let’s suppose we need n such slabs than
\[
  {\text{n}}\,{{ \times }}\,{\text{600 = 90000}} \\
  {{n}}\,{\text{ = }}\,\dfrac{{{\text{90000}}}}{{{\text{600}}}}\,{\text{ = }}\,\dfrac{{{\text{900}}}}{{\text{6}}}\,{\text{ = }}\,{\text{150}}\,{\text{unit}} \\
\]
Hence, we need 150 such slabs Option no. B is the correct answer.

Note: One common mistake students can do without converting into a similar unit they can solve. In this they will get the wrong answer. Room is in square form so use the area of square formula.