Ivan Shishkin, Rye (1878)

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On camels and dromedaries

by Catalpa·
11
Difficulty scaleÉchelle de difficulté

This score reflects both the level of the required concepts and the difficulty of the solution.Ce score tient compte à la fois du niveau des notions nécessaires et de la difficulté de la résolution.

  1. 110First steps / middle schoolPremiers pas / collège
  2. 1125Beginner / high schoolDébutant / lycée
  3. 2650Intermediate / undergraduateIntermédiaire / licence
  4. 5170Advanced / graduateAvancé / master
  5. 7190Expert / specializedExpert / spécialisé
  6. 91100Research levelNiveau recherche
These levels are approximate guides.Ces niveaux sont des repères approximatifs.
·
English
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A herd of dromedaries and camels is walking in the desert. There are 60 animals and 95 humps. How many camels are there? And how many dromedaries?

P.S.: We assume here that they could be in the same herd even though it is highly impossible, as they don’t live on the same continent!

Reminder: dromedaries have one hump and camels two.
camel and dromedary

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Solutions

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Solution by Ancient Tree

Discussions1 useful vote

Let dd be the number of dromedaries, and cc be the number of camels.
There are 60 animals in total, so d+c=60d+c=60.
Because dromedaries each have one hump, and camels two, the total number of humps is d+2c=95d+2c=95.

This is a linear system with two unknowns, cc and dd:
{d+c=60d+2c=95\left\{\begin{array}{l} d+c=60 \\ d+2 c=95 \end{array}\right.To solve it, we could subtract the first line from the second line, obtaining c=35c=35. Plugging this back into the first line gives d=60c=6035=25d=60-c=60-35=25.

Therefore, there are 25 dromedaries and 35 camels.

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