Practise Using Simple Formulae

Sometimes in maths, numbers can be replaced by letters but do not be put off by letters!

Letters are used for a special type of maths, called algebra.

When we use algebra, we use 'formulae'.

A formula is a concise, simple way of showing information with symbols.

There are lots of formulae in maths to find.

For example: area, perimeter and circumference. 

Example 1

If a = 6, b = 3 and c = 7, calculate the value of:

1. a + b             

2. a - b        

3. c + b - a 

Answer

1. a + b = 6 + 3 = 9 

2. a - b  = 6 - 3 = 3

3. c + b - a  = 7 + 3 - 6 = 4

There are some rules to remember when using formulae.

We write:

2 x a as 2a

a x b = ab

a ÷ b as a/b

Example 2

If p = 6, q = 12, r = 4 and s = 3 calculate the value of:

1. rs         

2. 2r + 3s           

3. s/3

Answer

1. rs = r x s  = 4 x 3 = 12

2. 2r + 3s  = 2 x r + 3 x s = 2 x 4 + 3 x 3   =8 + 9 = 17

3. s/3 = 3 ÷  3  = 1

How do you feel about having a go at some questions now?