David drove a distance (d) of 187 km, correct to 3 significant figures.

He used 28 litres of petrol (p), correct to 2 significant figures.

The petrol consumption (c) of a car, in km per litre, is given by the formula

C=

d

р

By considering bounds, work out the value of c for David's journey

to a suitable degree of accuracy.

You must show all your working and give a reason for your final answer.

Answer: 6.68km/litre

Step-by-step explanation:

Distance (d) = 187km (to 3 significant figures)

Petrol (p) = 28litres (to 2 significant figures)

A number, x, rounded to 1 significant figure is 200

Write down the error interval for x

Calculating the lower and upper bound for both 'd' and 'p'

Upper bound 'd' = 187.5km

Lower bound 'd' = 186.5km

Upper bound 'p' = 28.5km

Lower bound 'p' = 27.5km

Therefore,

Petrol consumption (C) = d/p

Upper C = 187.5 / 28.5 = 6.57894

Lower C = 186.5 / 27.5 = 6.781818

Accuracy answer for C = (6.57894 + 6.781818) / 2 = 6.680379

= 6.68km / litre (to 3 significant figures)

To achieve a reasonable level of accuracy, the upper and lower bounds of P and D was used to calculate C, which was then averaged.

Using 3 significant figures ensure that we capture the C better, instead of early rounding.