Math Problem Statement

The sum of the areas of all six faces of a cuboid is 322 cm². If its dimensions are in the ratio 1:2:3, find its length, breadth, and height

Solution

Let the dimensions of the cuboid be represented by:

  • Length = ll
  • Breadth = bb
  • Height = hh

The sum of the areas of the six faces of a cuboid is given by the formula:

2(lb+bh+hl)2(lb + bh + hl)

We are told that the sum of the areas is 322 cm², so:

2(lb+bh+hl)=3222(lb + bh + hl) = 322

Dividing both sides by 2:

lb+bh+hl=161lb + bh + hl = 161

Next, the dimensions are in the ratio 1:2:3, so we can express ll, bb, and hh in terms of a common variable xx:

l=x,b=2x,h=3xl = x, \quad b = 2x, \quad h = 3x

Substituting these into the equation lb+bh+hl=161lb + bh + hl = 161:

x(2x)+2x(3x)+3x(x)=161x(2x) + 2x(3x) + 3x(x) = 161

Simplifying:

2x2+6x2+3x2=1612x^2 + 6x^2 + 3x^2 = 161

11x2=16111x^2 = 161

Solving for x2x^2:

x2=16111=14.636x^2 = \frac{161}{11} = 14.636

Taking the square root of both sides:

x14.6363.83x \approx \sqrt{14.636} \approx 3.83

Now that we have x3.83x \approx 3.83, we can find the dimensions:

  • Length l=x3.83l = x \approx 3.83 cm
  • Breadth b=2x2×3.837.66b = 2x \approx 2 \times 3.83 \approx 7.66 cm
  • Height h=3x3×3.8311.49h = 3x \approx 3 \times 3.83 \approx 11.49 cm

Thus, the dimensions of the cuboid are approximately:

  • Length = 3.83 cm
  • Breadth = 7.66 cm
  • Height = 11.49 cm

Would you like further details or clarifications? Here's a set of related questions:

  1. How does the surface area formula for a cuboid derive from its face areas?
  2. How can the ratio of dimensions affect the calculation of surface area?
  3. What is the significance of the value xx in the context of cuboid dimensions?
  4. How can we solve this problem if the dimensions were in a different ratio, say 2:3:4?
  5. How would the calculation change if the cuboid's volume was also given?

Tip: When dealing with ratios in geometry, always express the variables in terms of a common factor before proceeding with the equation to simplify the process.

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Math Problem Analysis

Mathematical Concepts

Algebra
Surface Area of a Cuboid
Ratio and Proportions
Quadratic Equations

Formulas

Surface area of a cuboid: 2(lb + bh + hl)
Ratio of dimensions: l:b:h = 1:2:3

Theorems

Surface Area Theorem for Cuboids
Solving Quadratic Equations

Suitable Grade Level

Grades 8-10