Задачка про африканскую девочку
 

An African girl lives 6 km away from the nearest water source. Carrying two empty 5 litre canisters she can travel 4 km per hour on foot. When the canisters are filled with water she can walk only 2 km per hour. She needs 20 litres of water a day for drinking, cooking and washing.
How many hours does the girl spend fetching water instead of going to school?

9 часов + набор воды и тому подобное