Using inverse operations to solve one-step equations involving multiplication and division.
Imagine you are at a pizza party where the total bill was 8. How many friends were there? You just solved a mystery equation in your head!
In algebra, an equation is like a balanced scale. Whatever you do to one side, you must do to the other to keep it level. To solve for a variable (like ), we need to get it all by itself. We do this using inverse operations, which are operations that 'undo' each other. Think of it as the 'undo' button on your computer! The inverse of multiplication is division, and the inverse of division is multiplication. By applying these opposites, we can peel away the numbers surrounding our variable until the mystery is solved.
Quick Check
If an equation tells you to multiply a variable by 10, what operation should you use to 'undo' it?
Answer
Division (specifically, dividing by 10).
When you see an equation like , it means '5 times some number equals 30.' To isolate the variable , we need to get rid of the 5. Since the 5 is currently being multiplied by , we use the inverse operation: division. We divide both sides of the equation by 5. This keeps the scale balanced while leaving all alone on one side. Always remember: what you do to the left, you must do to the right!
Solve for :
Quick Check
Solve for in the equation .
Answer
Division equations look like fractions, such as . This means 'some number divided by 2 equals 10.' To set free, we use the inverse of division: multiplication. By multiplying both sides by the denominator (the bottom number), we cancel out the division. It is like unlocking a cage to let the variable out!
Solve for :
1. Identify the operation: is being divided by 5. 2. Use the inverse: Multiply both sides by 5. 3. Write the step: 4. Simplify: 5. Check: Does ? Yes!
Math isn't just about and ; it's about solving real problems. When reading a story, look for keywords. 'Each' or 'per' often suggest multiplication. 'Split' or 'shared equally' often suggest division. Once you identify the total and the parts, you can write your equation and solve it just like the examples above.
A group of friends ran a relay race. They ran a total of 12 miles. If each friend ran 1.5 miles, how many friends () were in the group?
1. Write the equation: 2. Identify the inverse: Divide by 1.5. 3. Calculate: 4. Solve: 5. Conclusion: There were 8 friends in the group.
What is the first step to solve ?
Solve for :
In the equation , the variable is equal to 2.
Review Tomorrow
In 24 hours, try to explain to a friend or family member why we have to do the same thing to both sides of an equation.
Practice Activity
Look at a grocery receipt. If you bought 4 identical items and know the total cost, try writing a multiplication equation to find the price of one item!