Substitution
What is substitution?
- Substitution means replacing a letter (variable) in a formula with a given number
How do I substitute numbers into a formula?
- Write down the formula
- Replace (substitute) the letters in the formula with the given numbers
- If substituting in a negative number, it is important to put brackets around it
- For example, (-3)
- If substituting in a negative number, it is important to put brackets around it
- Simplify any numerical calculations
- Calculate the final value
- Sometimes the result is an equation which you can then solve
Examiner Tip
- In the calculator paper, use your calculator to work out the final value.
- Don't forget to type out brackets around any substituted negative numbers!
Worked example
Substitute the numbers given
Use brackets () around negative numbers
Complete the calculation
Show every step of working, following the order of operations correctly
Substitute the values you are given for and into the formula
Simplify
Solve the resulting equation to find the value of
Start by subtracting 8 from both sides
Divide both sides by 2