Chapter 8: Problem 68
PREREQUISITE SKILL Solve each proportion. $$ \frac{7}{25}=\frac{a}{5} $$
Short Answer
Expert verified
The solution is \( a = \frac{7}{5} \).
Step by step solution
01
Identify the Cross Products
In a proportion \( \frac{a}{b} = \frac{c}{d} \), the cross products are equal, meaning \( a \cdot d = b \cdot c \). Let's express the cross products for our proportion \( \frac{7}{25} = \frac{a}{5} \). This means that \( 7 \times 5 = 25 \times a \).
02
Calculate the Cross Products
Multiply the known values to find one of the cross products: \( 7 \times 5 = 35 \). Now, you have the equation \( 35 = 25 \times a \).
03
Solve for the Unknown Variable
To find \( a \), divide both sides of the equation by 25: \( a = \frac{35}{25} \).
04
Simplify the Result
Simplify \( \frac{35}{25} \) by finding the greatest common divisor of 35 and 25, which is 5. Divide the numerator and denominator by 5: \( a = \frac{35 \div 5}{25 \div 5} = \frac{7}{5} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Cross Multiplication
Cross multiplication is a simple technique used to solve equations involving proportions. When you have a proportion like \( \frac{a}{b} = \frac{c}{d} \), cross multiplication allows you to set these fractions equal by multiplying crosswise. This means you multiply the numerator of one fraction by the denominator of the other.
- For \( \frac{7}{25} = \frac{a}{5} \), cross multiply like this: \( 7 \times 5 \) and \( 25 \times a \).
- The result is the equation \( 35 = 25a \).
Simplifying Fractions
Simplifying fractions is an important step in solving proportion problems, as it makes the answer easy to understand. A fraction is in its simplest form when the numerator and the denominator have no common factors other than 1. To simplify a fraction, you divide both the numerator and the denominator by their greatest common divisor (GCD).Take the fraction \( \frac{35}{25} \) for our problem, for instance:
- First, identify the GCD of the numerator and the denominator, which is 5.
- Then, divide both the numerator (35) and the denominator (25) by 5.
- The result is the fraction \( \frac{7}{5} \), which is already simplified.
Greatest Common Divisor
The greatest common divisor (GCD) is a crucial concept when simplifying fractions, especially in mathematical problems involving proportions. The GCD is the largest number that divides both the numerator and the denominator without leaving a remainder.Here's how you find the GCD for the fraction \( \frac{35}{25} \):
- List the factors of 35 (1, 5, 7, 35) and the factors of 25 (1, 5, 25).
- Find the largest number that appears in both lists. Here, that number is 5.