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Question

Identical square slabs are used to pave the floor of a room, $4.5 \text{ m}$ long and $1.5 \text{ m}$ broad. Find the minimum number of such slabs that will be needed to pave the floor.

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
$3$

Finding Minimum Square Slabs for Paving

To find the minimum number of identical square slabs needed to pave a rectangular floor, we need to determine the largest possible side length for the square slab. This side length must perfectly divide both the length and the breadth of the room.

Calculating Largest Square Slab Size

The largest possible side length for the square slab is the Greatest Common Divisor (GCD) of the room's dimensions.

  • Room Length = $4.5 \text{ m}$
  • Room Breadth = $1.5 \text{ m}$

We need to find the GCD of $4.5$ and $1.5$.

Notice that $4.5$ is exactly $3$ times $1.5$. Therefore:

$ \text{GCD}(4.5, 1.5) = 1.5 \text{ m} $

So, the largest possible identical square slab that can be used has a side length of $1.5 \text{ m}$.

Calculating Number of Slabs

Now, we calculate how many slabs fit along the length and breadth of the room.

  • Number of slabs along the length = $\frac{\text{Room Length}}{\text{Slab Side Length}} = \frac{4.5 \text{ m}}{1.5 \text{ m}} = 3$
  • Number of slabs along the breadth = $\frac{\text{Room Breadth}}{\text{Slab Side Length}} = \frac{1.5 \text{ m}}{1.5 \text{ m}} = 1$

The total minimum number of slabs is the product of the number of slabs along the length and breadth.

$ \text{Total Slabs} = (\text{Number along length}) \times (\text{Number along breadth}) $

$ \text{Total Slabs} = 3 \times 1 = 3 $

Therefore, the minimum number of identical square slabs needed is 3.

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Important Questions from LCM and HCF

  1. The HCF and LCM of two numbers are 12 and 72, respectively. If the ratio of the two numbers is 2 ∶ 3, then the larger of the two numbers is:

  2. Find the greatest number that will divide 43, 91 and 183 so as to leave the same remainder in each case.

  3. Joseph visits the club on every 5 th day, Harsh visits on every 24 th day, while Sumit visits on every 9 th day. If all three of them met at the club on a Sunday, then on which day will all three of them meet again?

  4. What is the least number which when divided by 12,20 and 24 leaves in each case a remainder of 8?

  5. Which of the following is a pair of co-primes?

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