Combine rational number operations and proportional reasoning to solve complex equations.
Have you ever wondered how architects shrink a massive skyscraper down to a tiny, perfect 3D model? It’s all about maintaining the exact same proportions using multi-step equations!
When equations look messy because of fractions, we can use a 'magic' trick to simplify them: multiply every term by the Least Common Denominator (LCD). This 'clears' the fractions, leaving you with whole numbers that are much easier to manage. If you are dealing with decimals, you can do something similar by multiplying by powers of 10 (like 10, 100, or 1000) to shift the decimal point. Remember, the Golden Rule of Algebra still applies: whatever operation you perform on one side of the equation, you must perform on the other side to keep the scale balanced.
Solve for :
1. Identify the denominator, which is . 2. Multiply every term by to clear the fraction: . 3. Simplify: . 4. Subtract from both sides: .
Quick Check
What is the first step to 'clear' the denominator in the equation ?
Answer
Multiply every term in the equation by 5.
Sometimes, a variable is 'trapped' inside parentheses. To set it free, we use the Distributive Property: . When the number outside the parentheses is a fraction or a decimal, the process is the same. Be extra careful with negative signs! If you multiply a negative number across parentheses, it flips the sign of every term inside. Once the parentheses are gone, you can combine like terms and solve the equation using standard inverse operations (addition/subtraction, then multiplication/division).
Solve for :
1. Distribute to both terms inside the parentheses: . 2. Simplify the multiplication: . 3. Add to both sides: . 4. Divide both sides by : .
Quick Check
When solving , what is the equation after the distributive step?
Answer
A proportion is an equation stating that two ratios are equal, such as . These are common in real-world scaling, like maps or recipes. To solve a complex proportion, we use cross-multiplication: . This effectively clears both denominators at once! If the numerator or denominator contains an expression (like ), treat it as a single unit by putting it in parentheses before you multiply. This ensures you distribute correctly.
Solve for :
1. Cross-multiply: . 2. Distribute on both sides: . 3. Subtract from both sides to collect variables: . 4. Add to both sides to isolate : .
Solve for :
What is the value of in the proportion ?
In the equation , the distributed form is .
Review Tomorrow
In 24 hours, try to explain to a friend how 'clearing the denominator' works and why we use the LCD.
Practice Activity
Find a cooking recipe and try to 'scale it up' by 1.5. Write an equation to find the new amount for an ingredient that originally called for cup.