Math Problem Statement

Les deux prismes illustrés ci-dessous ont le même volume. Quel est le binôme représentant la mesure manquante dans le prisme à base rectangulaire?

Solution

Let's analyze the problem from the uploaded image:

We are tasked with finding the missing dimension (a binomial) for the rectangular prism on the right, given that both prisms have the same volume.


Step 1: Volume of the Hexagonal Prism (Left Prism)

The volume of the left prism is calculated as: Volume=Area of Base×Height\text{Volume} = \text{Area of Base} \times \text{Height}

Base Area of the Hexagonal Prism:

The base of the hexagonal prism consists of a regular hexagon divided into six equilateral triangles.

Each equilateral triangle has a side length of 6b6b and an area formula: Area of one triangle=34×(side)2\text{Area of one triangle} = \frac{\sqrt{3}}{4} \times (\text{side})^2

So, the total area of the hexagon is: Area of Hexagon=6×34×(6b)2=6×34×36b2\text{Area of Hexagon} = 6 \times \frac{\sqrt{3}}{4} \times (6b)^2 = 6 \times \frac{\sqrt{3}}{4} \times 36b^2 Area of Hexagon=543b2\text{Area of Hexagon} = 54\sqrt{3}b^2

Height of the Hexagonal Prism:

The height is given as 8cm8 \, \text{cm}.

Total Volume of the Hexagonal Prism:

VolumeHexagonal Prism=543b2×8=4323b2\text{Volume}_{\text{Hexagonal Prism}} = 54\sqrt{3}b^2 \times 8 = 432\sqrt{3}b^2


Step 2: Volume of the Rectangular Prism (Right Prism)

The volume of the rectangular prism is also given as: VolumeRectangular Prism=Base Area×Height\text{Volume}_{\text{Rectangular Prism}} = \text{Base Area} \times \text{Height}

Base Area of the Rectangular Prism:

The base area is: Base Area=5×(4b)=20b\text{Base Area} = 5 \times (4b) = 20b

Total Volume of the Rectangular Prism:

The height of the rectangular prism is unknown, represented as ??. Let this height be xx. Then: VolumeRectangular Prism=20b×x=20bx\text{Volume}_{\text{Rectangular Prism}} = 20b \times x = 20bx


Step 3: Equating the Volumes

Since the volumes of both prisms are equal: 4323b2=20bx432\sqrt{3}b^2 = 20bx

Solve for xx: x=4323b220bx = \frac{432\sqrt{3}b^2}{20b} x=4323b20x = \frac{432\sqrt{3}b}{20} x=21.63bx = 21.6\sqrt{3}b


Step 4: Representing the Missing Dimension

The missing height of the rectangular prism is: x=21.63bx = 21.6\sqrt{3}b


Would you like a detailed explanation of any of the steps or further simplification? 😊


Related Questions:

  1. How is the volume of a hexagonal prism derived in general?
  2. Why does the base of a hexagonal prism consist of six equilateral triangles?
  3. What is the relationship between the area of a hexagon and its side length?
  4. How would the solution change if one of the bb-values were different?
  5. Could you calculate the exact numerical value of the missing height for b=1b = 1?

Tip:

Always verify that units and terms cancel correctly when equating expressions—this ensures your algebraic manipulations are valid.

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Math Problem Analysis

Mathematical Concepts

Volume of Prisms
Equating Volumes
Simplification of Expressions

Formulas

Volume = Base Area × Height
Area of a Hexagon = 6 × (√3/4) × side^2
Volume of Hexagonal Prism = Base Area × Height
Volume of Rectangular Prism = Base Area × Height

Theorems

Equating Volumes of Solids

Suitable Grade Level

Grades 10-12