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?
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