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Washing Elephants

Age 11 to 14
ShortChallenge Level Yellow starYellow starYellow star
Secondary curriculum
  • Problem
  • Solutions


Answer: 22$\frac29$ minutes


Scaling up to more elephants
Mary: 50 minutes   1 elephant          200 minutes   4 elephants

Nigel: 40 minutes   1 elephant          200 minutes   5 elephants

Together:  200 minutes    9 elephants
             200$\div$9 minutes  1 elephant
             200$\div$9 = 22$\frac29$


Seeing how much of the elephant is clean after 10 minutes (or 5, or 20, etc)
Mary:  50 minutes   1 elephant            10 minutes   $\frac15$ elephant

Nigel:  40 minutes   1 elephant            10 minutes   $\frac14$ elephant

Together:                                            10 minutes   $\frac15+\frac14=\frac9{20}$ elephant
                                                       10$\div$9 minutes    $\frac1{20}$ elephant
                                                      200$\div$9 minutes    1 elephant
                                                      200$\div$9 = 22$\frac29$



 

 

 

You can find more short problems, arranged by curriculum topic, in our short problems collection.

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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