/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 90 A rectangular piece of cardboard... [FREE SOLUTION] | 91Ó°ÊÓ

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A rectangular piece of cardboard whose length is twice its width is used to construct an open box. Cutting a 1 foot by 1 foot square off of each corner and folding up the edges will yield an open box. If the desired volume is 12 cubic feet, what are the dimensions of the original rectangular piece of cardboard?

Short Answer

Expert verified
The dimensions of the original cardboard are 4 ft (width) and 8 ft (length).

Step by step solution

01

Understand the Problem

We have a rectangular piece of cardboard whose length is twice its width. We remove a 1-foot square from each corner and fold up the sides to create an open box with a volume of 12 cubic feet. We need to find the original dimensions of the cardboard.
02

Define Variables

Let the width of the piece of cardboard be denoted by \( w \). Since the length is twice the width, we denote the length as \( 2w \). The volume formula for the box is given as Volume = Length \( \times \) Width \( \times \) Height, which should be 12 cubic feet.
03

Deduce the Box Dimensions

When we cut 1-foot squares from each corner and fold, the new dimensions of the box are: the length becomes \( 2w - 2 \) (since 1 foot is cut from both ends), the width becomes \( w - 2 \), and the height is 1 foot (the cut square size).
04

Set Up the Volume Equation

The equation for the volume of the box is:\[(2w - 2)(w - 2)(1) = 12\]This simplifies to:\[(2w - 2)(w - 2) = 12\]
05

Solve the Equation

Expand and simplify the equation:\[(2w - 2)(w - 2) = 12 \2w^2 - 4w - 2w + 4 = 12 \2w^2 - 6w + 4 = 12\]Subtract 12 from both sides:\[2w^2 - 6w - 8 = 0\]Divide by 2:\[w^2 - 3w - 4 = 0\]Factor or use the quadratic formula to find \( w \):\[(w - 4)(w + 1) = 0\]The solutions are \( w = 4 \) and \( w = -1 \). Since a negative width doesn't make sense, \( w = 4 \).
06

Find the Length

With \( w = 4 \), substitute back to find the length:\[2w = 2 \times 4 = 8\]
07

Verify the Dimensions

The original dimensions of the cardboard are width = 4 ft and length = 8 ft. Check: Cut out two 1-foot squares, making length of the box \( 8 - 2 = 6 \) ft, width \( 4 - 2 = 2 \) ft, and height 1 ft. Volume is \( 6 \times 2 \times 1 = 12 \) cubic feet, confirming our calculations.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Cardboard Dimensions
When working with rectangular pieces of cardboard, understanding the initial dimensions is essential. In this exercise, we start with a piece of cardboard where the length is twice the width. This means if the width is measured at, say, 4 feet, the length will automatically be 8 feet because it is calculated as double the width.
Once the dimensions are established, the next step involves altering the cardboard. In this case, we cut a 1-foot by 1-foot square from each of the four corners. This allows us to create flaps that can be folded up to form the sides of the box. By removing these squares, the dimensions of the box's base decrease. So, the potential new length becomes the original length minus 2 feet (1 foot cut from each end), and the width becomes the original width minus 2 feet.
Understanding how these cuts change the cardboard's dimensions is crucial for calculating the resulting box dimensions accurately.
Quadratic Equation
Quadratic equations are powerful tools for solving problems involving dimensions, particularly when those problems aren't straightforward. When we try to create a box from a piece of cardboard by cutting and folding, we often end up simplifying the problem into a quadratic equation to solve for unknown dimensions.
The quadratic equation in this context helps us determine the original width of the cardboard. The expression \[ (2w-2)(w-2) = 12 \] comes from setting up the volume equation after cutting out the corners. Expanding this results in a quadratic equation:\[ 2w^2 - 6w + 4 = 12 \].
After simplifying and rearranging, we get:\[ w^2 - 3w - 4 = 0 \].
The solutions to this equation, typically achieved by factoring or using the quadratic formula, represent the potential values for the width. In our example, only positive solutions make sense, ultimately giving us the width as 4 feet.
Volume Calculation
Calculating the volume of a three-dimensional object like a box requires knowing its length, width, and height. In the context of our cardboard box, once we've altered the cardboard, we need to ensure it achieves the right volume, which is specified as 12 cubic feet.
The formula for volume is straightforward: \[ \text{Volume} = \text{Length} \times \text{Width} \times \text{Height} \].
In this problem, once the squares are cut out and the sides are folded, the box's dimensions are adjusted to \[ 6 \times 2 \times 1 \] feet. Here, 6 feet is the new length, 2 feet is the new width, and 1 foot is the height. Multiplying these gives the desired volume of 12 cubic feet.
This formulation confirms our adjustment was correct, as maintaining these dimensional relationships ensures the box achieves the necessary size to meet the specified volume.

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