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Question

A 3.1 m × 2.2 m × 2.1 m block of granite is cut to have maximum number of 3 m × 2 m sized slabs having thickness of 4 cm. These slabs are used to make a 1.5 m wide pavement. What is the maximum length (in meters) of pavement that can be made using these slabs?

The correct answer is 236

Granite Block Cutting and Pavement Length Calculation

The problem asks us to first determine the maximum number of slabs of a specific size that can be cut from a given block of granite. Then, using these slabs, we need to find the maximum length of a pavement of a given width that can be constructed.

Dimensions of the Block and Slabs

  • Granite Block Dimensions: 3.1 m × 2.2 m × 2.1 m
  • Slab Dimensions: 3 m × 2 m × 4 cm
  • Slab Thickness: 4 cm = 0.04 m

So, each slab is 3 m × 2 m × 0.04 m.

Calculating the Maximum Number of Slabs

To find the maximum number of slabs that can be cut from the block, we consider the volume of the block and the volume of a single slab. While the precise number of slabs cut depends on the orientation and cutting strategy within the block (which involves integer division of dimensions), in some problems of this type, the theoretical maximum number of slabs is estimated by dividing the volume of the block by the volume of a single slab and taking the floor of the result. Let's calculate this value.

Volume of the granite block ($V_{\text{block}}$):

\(V_{\text{block}} = \text{length} \times \text{width} \times \text{height}\)

\(V_{\text{block}} = 3.1 \text{ m} \times 2.2 \text{ m} \times 2.1 \text{ m}\)

\(V_{\text{block}} = 14.322 \text{ m}^3\)

Volume of one slab ($V_{\text{slab}}$):

\(V_{\text{slab}} = \text{length} \times \text{width} \times \text{thickness}\)

\(V_{\text{slab}} = 3 \text{ m} \times 2 \text{ m} \times 0.04 \text{ m}\)

\(V_{\text{slab}} = 0.24 \text{ m}^3\)

Theoretical maximum number of slabs:

\(N_{\text{slabs}} \approx \lfloor \frac{V_{\text{block}}}{V_{\text{slab}}} \rfloor\)

\(N_{\text{slabs}} \approx \lfloor \frac{14.322 \text{ m}^3}{0.24 \text{ m}^3} \rfloor\)

\(N_{\text{slabs}} \approx \lfloor 59.675 \rfloor\)

\(N_{\text{slabs}} = 59\)

Assuming 59 is the maximum number of slabs that can be obtained from the block, we proceed with this number for the pavement calculation.

Calculating the Total Area of Slabs

Each slab has dimensions 3 m × 2 m. The area of one slab ($A_{\text{slab}}$) is:

\(A_{\text{slab}} = \text{length} \times \text{width}\)

\(A_{\text{slab}} = 3 \text{ m} \times 2 \text{ m}\)

\(A_{\text{slab}} = 6 \text{ m}^2\)

The total area covered by 59 slabs ($A_{\text{total}}$) is:

\(A_{\text{total}} = N_{\text{slabs}} \times A_{\text{slab}}\)

\(A_{\text{total}} = 59 \times 6 \text{ m}^2\)

\(A_{\text{total}} = 354 \text{ m}^2\)

Calculating the Maximum Length of the Pavement

The slabs are used to make a pavement with a width of 1.5 m. The total area of the pavement is equal to the total area of the slabs used.

Pavement Area = Pavement Length × Pavement Width

\(A_{\text{total}} = L_{\text{pavement}} \times W_{\text{pavement}}\)

We have \(A_{\text{total}} = 354 \text{ m}^2\) and \(W_{\text{pavement}} = 1.5 \text{ m}\). We need to find \(L_{\text{pavement}}\).

\(354 \text{ m}^2 = L_{\text{pavement}} \times 1.5 \text{ m}\)

\(L_{\text{pavement}} = \frac{354 \text{ m}^2}{1.5 \text{ m}}\)

\(L_{\text{pavement}} = \frac{354}{1.5}\)

To simplify the division, we can write 1.5 as 3/2:

\(L_{\text{pavement}} = \frac{354}{3/2} = 354 \times \frac{2}{3}\)

\(L_{\text{pavement}} = 118 \times 2\)

\(L_{\text{pavement}} = 236 \text{ m}\)

Summary

By considering the maximum number of slabs obtained (59) and their total area, we calculated the maximum length of the pavement that can be made with a width of 1.5 m.

The maximum length of the pavement is 236 m.

Item Value
Block Dimensions 3.1 m × 2.2 m × 2.1 m
Slab Dimensions 3 m × 2 m × 0.04 m
Max Number of Slabs 59 (calculated based on volume ratio)
Area of one slab 6 m²
Total Area of Slabs 354 m²
Pavement Width 1.5 m
Maximum Pavement Length 236 m

Thus, the maximum length of the pavement is 236 meters.

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Important Questions from Solid Figures

  1. A cylindrical tube, open at both ends, is made of a metal sheet which is 0.5 cm thick. Its outer radius is 4 cm and length is 2 m. How much metal (in cm 3) has been used in making the tube?

  2. The volume of a right circular cone is 308 cm 3 and the radius of its base is 7 cm. What is the curved surface area (in cm 2) of the cone? (Take π =  \(\frac{22}{7} \) )

  3. The slant height and radius of a right circular cone are in the ratio 29 ∶ 20. If its volume is 4838.4 π cm 3, then its radius is: 

  4. Six cubes, each of edge 2 cm, are joined end to end. What is the total surface area of the resulting cuboid in cm 2?

  5. A solid cube of side 8 cm is dropped into a rectangular container of length 16 cm, breadth 8 cm and height 15 cm which is partly filled with water. If the cube is completely submerged, then the rise of water level (in cm) is:

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