Eratosthenes and the Arc

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Instructions

On the next page there are 25 different animals and your challenge is to get them onto Eratosthenes’s Arc on page 4.

However, unlike Noah’s Ark, not all the animals are in pairs. How many animals can you find of the same type? For example how many insects can you find?

Count each animal of the same type and then order them in their groups from the least to the greatest and a message will be revealed

When counting, don’t forget to include the gold animals in the picture - can you see them? Make sure you add them to your groups.

Look out for the Alligator, Newt, Irish Wolfhound, Numbat, Yak, Ibis, Eagle and the lovely Earwigs.

For those familiar with Maths Detectives, the title always holds a great clue to help you solve the puzzle!

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Ant

Newt

Insect

Mouse

Alligator

Lion

Snake

Whale

Elephant

Narwhal Tiger

Iguana

Numbat

Penguin

Rabbit

Irish Wolfhound

Monkey

Eagle

Bat

Yak

Panda

Rhinoceros

Ibis

Meerkat

Earwig

Eratosthenes’s Animals

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Teacher’s guideThe puzzle reveals the sequence of all prime numbers less than 100.Reception to Year 2: Practice counting and identifying the different animals, including finding the golden ones. What is a Yak and a Numbat? Where would you most likely findthem? Discuss which animals you’ve found who can survive on land and in water.

Years 3 and 4: Count the different animals and try sorting the groups from the least (Ant) to highest number (Earwig). Children may be familiar with prime numbers. Explain thatprimes are numbers that are only divisible only by itself and 1.

Years 5 and 6: Count the numbers and see if children can spot the prime sequence when ordering the groups from least to the highest. The sequence of the groups are all prime numbers. Try and see if they can predict the number of the next group. Show them the sieve of Eratosthenes.

The puzzle is quite difficult and relies on using the exact name of the animals. For example, Irish Wolfhound.

Good luck – Any questions, please visit mathsdetectives.com/primearc

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