Using Formulae

• By the end of the lesson, you should have a good understanding of:

• The usefulness of formulae• How to produce a formula• How to rearrange formulae to suit a situation

Taxi FareA taxi-driver charges a fixed rate of £2 per journey plus 50p per mile.

How much does it cost to travel 10 miles?£2£2 + + £0.50 £0.50 x 10 = £7x 10 = £7

Can you produce a formula for the cost of travel?

c = c = 22 + + 0.50.5dd(where c is the cost in £ and d is the distance in miles)

Taxi FareA taxi-driver charges a fixed rate of £2 per journey plus 50p per mile.

How far can you travel for £10?(£10 - (£10 - £2£2) / ) / £0.50 £0.50 = 16 miles= 16 miles

Can you produce a formula for the cost of travel?

d = (c - d = (c - 22) / ) / 0.50.5or: or: d = 2(c – d = 2(c – 22))

(where c is the cost in £ and d is the distance in miles)

Taxi FareA taxi-driver charges a fixed rate of £2 per journey plus 50p per mile.

c = c = 22 + + 0.50.5d d .c – 2 = 0.5dc – 2 = 0.5d

2(c – 2)= d 2(c – 2)= d .#

Changing the subject

1)

2)

3)

4)

a=, b=, c=

m1=, m2=, r=

v=, u=, a=, s=

u=, a=, t=

ms-1 ms-1

ms-2

m

m2s-2 m2s-2 ms-2m

In a formula, the dimension of the sides is always the same

s

ms-2

m1

s _m_ms-2

m

ms-1

s ms-2

s