Formulas are crucial in GCSE Maths (Higher Level) and are an essential algebra component. They enable you to solve problems and answer questions more efficiently by providing a framework for representing relationships between different quantities.

However, **sometimes you may be required to rearrange or manipulate these formulas to suit the specific needs of a problem.** It may be intimidating to take on this task, but with persistence and continual practice, you can eventually master it.

**Substitution is the first essential skill you need to understand when using formulas.** Substitution involves replacing the variable in a formula with its given value. For example, if we have the formula A = bh, where A represents the area of a rectangle, b represents the base, and h represents the height. We are given b = 4 and h = 5; we can substitute these values in the formula to find the area.

**Thus,** A = 4 × 5 = 20.

**The second essential skill is rearranging formulas.** To rearrange a formula, you must isolate the variable you are trying to find on one side of the equation. This involves using algebraic manipulation techniques such as adding, subtracting, multiplying, or dividing both sides of the equation by the same value. The goal is to end up with the variable you are trying to find on one side of the equation and everything else on the other side.

Let's consider the example of finding the radius of a cylinder when given its volume and height. We know that the formula for the volume of a cylinder is **V = πr ^{2}h, where V represents the volume, r represents the radius, and h represents the height.** To find

**r,**we need to rearrange the formula to isolate

**r**on one side of the equation. To do this, we can start by dividing both sides of the equation by πh, which gives us the following:

\(\frac{V}{(πh)} = {r}^{2}\)

To **isolate r,** we can take the square root of both sides of the equation, which gives us the following:

\(r = \sqrt\frac{V}{(πh)}\)

Thus, we have **successfully rearranged the formula to make r the subject** of the equation.

**Another example** could be finding the value of **x** in equation **2x + 5 = 13.** To isolate **x,** we need to subtract 5 from both sides of the equation to obtain the following:

**2x = 8**

**Next, we divide both sides by 2 to get:**

x = 4

Therefore, **the value of x is 4.**

In conclusion, mastering the skills of substitution and rearranging formulas is essential for success in GCSE Maths (Higher Level). With practice and a solid understanding of algebraic manipulation techniques, you can confidently solve problems and answer questions using formulas.

## Revision Quiz

To answer the questions correctly, **hover over each option and click to select it.** After you finish, click **'Submit'** to check your **score and see the correct answers and explanations.** Most questions will include an **explanation with the answer.** Please take the time to read the explanations accompanying the answers to your questions. Doing so will **give you a better overall understanding of the topic.** All the best!

## This topic is for Premium Plan subscribers only

Sign up now and upgrade your account to read the post and get access to the full library of learning topics for paying subscribers only.

Sign up now Already have an account? Sign in