using formulae 7

1.

Using expressions and
formulae
In this section you will ...
use the correct order of operations in algebraic expressions
•represent a situation either in words or as a formula
•change the subject of a formula.

2.

A formula is a
mathematical
rule that shows
the relationship
between two or
more quantities
(variables). It is a
rule that can be
written in letters
or words. The
plural of formula
is formulae.

3.

You can write, or derive, your own formulae to solve problems. An
example of a formula is F = ma.
In this formula, F is the subject of the formula. The variable F is
written on its own on the left hand side of the formula.
You may need to rearrange a formula to make a different variable
the subject. This is called changing the subject of the formula.

4.

5.

6.

7.

This is part of Dakarai’s
homework. He has
made a mistake in his
working.
Explain the mistake he
has made.
Work out the correct
answer.

8.

Deriving new
formula