Chapter 7: Problem 51
Find the value of \(x\) in each proportion. $$ \frac{x}{5}=\frac{8}{11} $$
Short Answer
Expert verified
x = \( \frac{40}{11} \)
Step by step solution
01
Understand the Proportion
We are given the proportion \( \frac{x}{5} = \frac{8}{11} \). Our task is to find the value of \( x \) that makes this equation true.
02
Set Up the Cross-Multiplication
In a proportion \( \frac{a}{b} = \frac{c}{d} \), cross-multiplication means \( a \cdot d = b \cdot c \). Apply this to our proportion: \( x \cdot 11 = 5 \cdot 8 \).
03
Solve the Equation for x
First multiply the right-hand side: \( 5 \cdot 8 = 40 \). So the equation becomes \( 11x = 40 \). Now, solve for \( x \) by dividing both sides by 11: \( x = \frac{40}{11} \).
04
Simplify the Result (if necessary)
Check if \( \frac{40}{11} \) can be simplified. In this case, since 40 and 11 have no common divisors, \( \frac{40}{11} \) is already in its simplest form.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cross-Multiplication
The concept of cross-multiplication is a handy method used in algebra to solve equations involving proportions. A proportion is an equation that states two ratios are equal. For example, in the exercise, the proportion given is \( \frac{x}{5} = \frac{8}{11} \).
To use cross-multiplication, you multiply each number in the numerator of one ratio by the denominator of the other, which allows you to eliminate the fractions and work with a simple equation. Here’s how you handle it:
To use cross-multiplication, you multiply each number in the numerator of one ratio by the denominator of the other, which allows you to eliminate the fractions and work with a simple equation. Here’s how you handle it:
- Identify the cross-products in the proportion. For \( \frac{x}{5} = \frac{8}{11} \), the cross-products are \( x \cdot 11 \) and \( 5 \cdot 8 \).
- You set these two cross-products equal to each other, forming the equation: \( x \cdot 11 = 5 \cdot 8 \).
Solving Equations
Once you’ve cross-multiplied, you're left with an equation that appears simpler to solve. In this example, you have: \( 11x = 40 \). Here, our only variable is \( x \), and our job is to isolate it to find its value.
Solving an equation generally involves:
Solving an equation generally involves:
- Performing operations that help isolate the variable on one side of the equation.
- Whatever operation you perform on one side, you must also perform on the other.
- \( x = \frac{40}{11} \)
Simplifying Fractions
When you reach a solution that is a fraction, as was \( x = \frac{40}{11} \) in this example, it is important to check if the fraction can be simplified further.
A simplified fraction is one in which the numerator and denominator have no factors in common except 1. The steps are:
A simplified fraction is one in which the numerator and denominator have no factors in common except 1. The steps are:
- Find the greatest common divisor (GCD) of the numerator and denominator.
- Divide the numerator and the denominator by the GCD.