Forum login

Not registered? Sign-up here it's free.

External links

• NCEA on TKI
• NZQA website

Mathematics 1.4 Apply linear algebra in solving problems

Using formulae

A formula is another word for a rule or equation that shows the relationship between different quantities. The plural of formula is formulae.

We can use formulae to work out values.

 e.g.   Use v = u + at to calculate v when u = 20, a = 10 and    
          t = 5      
          Answer: v   = 20 + 10 x 5
                            = 20 + 50
                            = 70

 e.g.   Use the formula C = 
          to convert 320°F to degrees Celsius (°C)

          Answer: C = 
                          = 
                            = 160°C

For more information and practice, see Formulae

Rearranging formulae

e.g.Make F the subject of the formula C =

           Answer:

           The subject of this formula is C because it is the
           letter on its own.

           Changing the subject of a formula is the same as
           solving an equation.

             C = 

            9C = 5(F – 32)    Multiply each side by 9 to undo
                                     the dividing by 9
          C = F - 32       Divide each side by 5 to undo
                                    multiplying by 5
    C + 32 = F            Add 32 to each side

              F = C + 32

For more information see:
Changing the subject of a formula - higher
Literal equations
Solving literal equations
Rearrangement of formulae.

Back to top