On the last page, we worked out that the meter below reads 68,232·0 kWh Let us work out what the bill would be if, a year earlier, the meter had read 64,822·5 kWh. Assume each unit of electricity costs £0.08.

Number of units used = 68,232·0 - 64,822·5 = 3,409·5 kWh

Total cost = £0.08 × 3,409·5 = £272.76