Chapter 10: Problem 58
Sign Dimensions. The base of a triangular sign is 4 in. longer than twice the height. The area of the sign is 255 in \(^{2} .\) Find the dimensions of the sign.
Short Answer
Expert verified
Height = 15 inches, Base = 34 inches.
Step by step solution
01
- Define Variables
Let the height of the triangular sign be denoted as h inches. The base of the triangular sign is given to be 4 inches longer than twice the height, so we can express the base as 2h + 4 inches.
02
- Write the Area Formula for a Triangle
Recall the formula for the area of a triangle: \[ \text{Area} = \frac{1}{2} \times \text{base} \times \text{height} \]. Given the area of the sign is 255 square inches, substitute the known values into the formula: \[ 255 = \frac{1}{2} \times (2h + 4) \times h \].
03
- Simplify the Equation
Simplify the area formula equation: \[ 255 = \frac{1}{2} \times (2h^2 + 4h) \] Multiply both sides by 2 to clear the fraction: \[ 510 = 2h^2 + 4h \]
04
- Rearrange the Equation
Rearrange the equation into standard quadratic form: \[ 2h^2 + 4h - 510 = 0 \]
05
- Solve the Quadratic Equation
Use the quadratic formula \[ h = \frac{-b \,\pm\, \sqrt{b^2 - 4ac}}{2a} \] where a = 2, b = 4, and c = -510. Substitute these values into the formula: \[ h = \frac{-4 \,\pm\, \sqrt{4^2 - 4 \times 2 \times (-510)}}{2 \times 2} \] Simplify under the square root: \[ h = \frac{-4 \,\pm\, \sqrt{16 + 4080}}{4} \] \[ h = \frac{-4 \,\pm\, 64}{4} \].This gives two solutions: \[ h = \frac{60}{4} = 15 \] and \[ h = \frac{-68}{4} = -17 \] Discard the negative value since height cannot be negative. Hence, h = 15 inches.
06
- Find the Base
Substitute h = 15 back into the expression for the base: \[ \text{base} = 2h + 4 = 2(15) + 4 = 34 \] inches.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
area of a triangle
Understanding the formula for the area of a triangle is crucial in solving geometry problems. The area of a triangle can be calculated using the formula:
- Area = \( \frac{1}{2} \times \text{base} \times \text{height} \)
- 255 = \( \frac{1}{2} \times \text{base} \times \text{height} \)
variable definition in algebra
In algebra, defining variables is a critical step in solving equations. Variables represent unknown values that we need to find. In this problem, we define:
Clear variable definitions simplify complex problems, making it easier to understand and solve equations.
- \(h\) as the height of the triangular sign
- \(2h + 4\) as the base of the triangular sign
Clear variable definitions simplify complex problems, making it easier to understand and solve equations.
solving equations
Solving equations, especially quadratic equations, is a fundamental skill in algebra. Here's a quick overview of how to approach it:1. **Simplify the Equation:** Once we substitute our variables into the area formula, we simplify the equation:
- 255 = \( \frac{1}{2} \times (2h + 4) \times h \)
- 510 = 2h² + 4h
- 2h² + 4h - 510 = 0
- \(h = \frac{-b \,\pm\, \sqrt{b² - 4ac}}{2a}\) where \(a = 2\), \(b = 4\), and \(c = -510\)
- \(h = 15\)
- \(h = -17\) (discarded as height cannot be negative)
- \(2h + 4 = 34\) inches