Math Problem Statement

Areas of two adjacent faces of a box in the shape of cuboid are 36c * m ^ 2 and 45c * m ^ 2 respectively. The measures (in cm) of length, breadth and height of the box are natural numbers. Find the ratio of the smallest possible volume of the box to the largest possible volume.

(a) 1:9

(b) 5:9

(c) 1:3

(d) 5:6

Solution

To solve this problem, we need to determine the length, breadth, and height of the cuboid box, and then find the ratio of the smallest possible volume to the largest possible volume.

Step 1: Understand the given information

Let the dimensions of the cuboid be ll (length), bb (breadth), and hh (height). We are given the areas of two adjacent faces:

  • Area 1 = lb=36c×m2lb = 36c \times m^2
  • Area 2 = bh=45c×m2bh = 45c \times m^2

Since c×m2c \times m^2 is a common factor, let's consider the equations without it for simplicity:

  • lb=36lb = 36
  • bh=45bh = 45

Step 2: Factorize the given areas

Factorize the numbers 36 and 45 to find the possible dimensions l,b,l, b, and hh.

  • 36=22×3236 = 2^2 \times 3^2
  • 45=32×545 = 3^2 \times 5

Now, let’s identify pairs of factors that could represent the possible lengths, breadths, and heights:

  • Possible values of ll and bb (from lb=36lb = 36) are (1,36),(2,18),(3,12),(4,9),(6,6)(1, 36), (2, 18), (3, 12), (4, 9), (6, 6).
  • Possible values of bb and hh (from bh=45bh = 45) are (1,45),(3,15),(5,9)(1, 45), (3, 15), (5, 9).

Step 3: Match the common dimension bb

We need to find a common value of bb from both equations.

  • If b=9b = 9, then l=4l = 4 (since 4×9=364 \times 9 = 36) and h=5h = 5 (since 9×5=459 \times 5 = 45).
  • If b=3b = 3, then l=12l = 12 (since 12×3=3612 \times 3 = 36) and h=15h = 15 (since 3×15=453 \times 15 = 45).

Step 4: Calculate volumes

The volume VV of a cuboid is given by V=l×b×hV = l \times b \times h.

  • For (l,b,h)=(4,9,5)(l, b, h) = (4, 9, 5), the volume is V1=4×9×5=180cm3V_1 = 4 \times 9 \times 5 = 180 \, \text{cm}^3.
  • For (l,b,h)=(12,3,15)(l, b, h) = (12, 3, 15), the volume is V2=12×3×15=540cm3V_2 = 12 \times 3 \times 15 = 540 \, \text{cm}^3.

Step 5: Find the ratio of the smallest volume to the largest volume

The smallest volume is 180cm3180 \, \text{cm}^3 and the largest volume is 540cm3540 \, \text{cm}^3. The ratio is: Ratio=180540=13\text{Ratio} = \frac{180}{540} = \frac{1}{3} So, the correct answer is 13\frac{1}{3}, which corresponds to option (c) 1:3.

Would you like more details on any part of this solution? Here are five related questions to further your understanding:

  1. How would the solution change if the areas given were different?
  2. Can you derive the same ratio using different factorization techniques?
  3. How do you determine which factorization pairs are valid for the dimensions of a cuboid?
  4. What if one of the faces' areas was a non-integer?
  5. How would the problem change if the box was a cube instead of a cuboid?

Tip: Always factorize the given values and try to match the common dimension when solving problems involving the dimensions of cuboids or other geometric shapes.

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Math Problem Analysis

Mathematical Concepts

Geometry
Factorization
Volumes of Cuboids

Formulas

Volume of a cuboid: V = l \times b \times h

Theorems

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Suitable Grade Level

Grades 7-9