Washing elephants

How long will it take Mary and Nigel to wash an elephant if they work together?
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative


Mary and Nigel look after elephants in a zoo.

Mary takes 50 minutes to wash an elephant and Nigel takes 40 minutes to wash an elephant.

If they wash an elephant together, how long will it take them?

This problem is taken from the World Mathematics Championships