Solving a Formula for a Variable
Learn solving a formula for a variable in Grade 9 math — Use inverse operations to isolate any variable in the formula. Part of Functions and Graphing for Grade 9.
Key Concepts
Property A formula is a type of literal equation. Use inverse operations to isolate any variable in the formula.
Examples Given the distance formula $d = rt$, solving for the rate gives $r = \frac{d}{t}$. Given $F = \frac{9}{5}C + 32$, solving for Celsius gives $C = \frac{5}{9}(F 32)$. Given the area of a circle $A = \pi r^2$, solving for the radius gives $r = \sqrt{\frac{A}{\pi}}$.
Explanation Formulas are like pre made recipes, but what if you need to figure out an ingredient amount instead of the final dish? That's when you rearrange the formula! If you know the circumference of a circle but need the radius, you solve the formula $C=2\pi r$ for $r$. This lets you plug in the numbers you have to find the one you need.
Common Questions
What is 'Solving a Formula for a Variable' in Grade 9 math?
Use inverse operations to isolate any variable in the formula. Use inverse operations to isolate any variable in the formula.
How do you solve problems involving 'Solving a Formula for a Variable'?
Use inverse operations to isolate any variable in the formula. Explanation Formulas are like pre-made recipes, but what if you need to figure out an ingredient amount instead of the final dish?.
Why is 'Solving a Formula for a Variable' an important Grade 9 math skill?
$$w = \frac{P - 2l}{2}$$ Common mistake tip: Many students try to handle multiplication or division before addition or subtraction.. In $P = 2l + 2w$, you must get rid of the `+ 2l` term before you can get rid of the `2` that's multiplied by the $w$.