**1. Why do I need to be able to substitute in algebra?**

Many jobs, such as engineering or those in science and research use formulae to make calculations.

For example, to change temperatures in degrees centigrade (used in Australia and New Zealand) to degrees fahrenheit (used in the US) the formula F = 9C/ 5 + 32 is used.

So if we wish to find the equivalent of 100

^{o}C (the boiling point of water) in degrees fahrenheit, wesubstitute100 for C in the formula:F = 9 × 100 / 5 + 32 = 212

So 100

^{o}C = 212^{o}F

**2. When working out the value of an expression using a substitution does the BEDMAS rule apply?**

Yes, the

BEDMASrule for the order that you do operations applies to all mathematics.

**3. What are common mistakes made when substituting?**

People forget that the

BEDMASrule for the order that you do operations applies toallmathematics.

Example: When substituting into a term like 5p^{2}there are two ways to try ot work this out. One is very wrong!

SubstitutionCalculationAnswerCorrect or Incorrect? Evaluate 5p^{2}when p =3 5 × (3×3) 45CORRECT (5 ×3)^{2} 225INCORRECT