A company has bikes for hire.
The cost, £C, to hire a bike for n days is given by the formula
C = 15 + (n − 1)
Write down the cost to hire a bike for 1 day.
£
[1 mark]
?
𝐶 = 15 + × (1 − 1) = 15 + 0 = 15
Special offer!
Hire a bike for £9 per day
(i)
(ii)
(iii)
Which is cheaper?
?
7 × £9 = £63; 𝐶 = 15 + × (7 − 1) = 15 + × 6 = 15 + = 15 + 40.5 = £55.50; £55.50 < £63
[3 marks]
The graph shows the cost to hire a bike for one to five days at a different company.

The cost, £C, to hire a bike for n days from this company is given by the formula
𝐶 = 𝑎 + 𝑏(𝑛 − 1)
Work out the values of a and b.
(i)
a =
[1 marks]
(ii)