Joan makes cups of tea and coffee at a lunch club - OCR - GCSE Maths - Question 14 - 2019 - Paper 1

Joan has boiled 10 litres of water in an urn which will contribute to her total requirement.

Thus, the amount of additional water needed is:

$14 ext{ litres} - 10 ext{ litres} = 4 ext{ litres}$

The kettle can boil 1.7 litres of water at a time. To find out how many times Joan needs to boil the kettle for the additional 4 litres, we divide the amount needed by the capacity of the kettle:

$ext{Number of boils} = \lceil \frac{4 ext{ litres}}{1.7 ext{ litres/kettle}} \rceil$

Calculating this gives:

$\frac{4}{1.7} \approx 2.35$

Since she cannot boil the kettle a fraction of a time, we round it up:

Joan needs to boil the kettle at least 3 times to provide the additional 4 litres.