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### Number and algebra

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### Working mathematically

### For younger learners

### Advanced mathematics

# The Pet Graph

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### How Big Are Classes 5, 6 and 7?

### Presenting the Project

### Real Statistics

Links to the University of Cambridge website
Links to the NRICH website Home page

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30 April (Primary), 1 May (Secondary)

30 April (Primary), 1 May (Secondary)

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Age 7 to 11

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Tina sent us her solution. She tackled the problem logically.

Only one child has a parrot at home, so the green bar must be parrots.

Fish+gerbils=dogs and if you try all the possibilities it must be the red bar for dogs, and the blue and yellow bars for fish and gerbils (but we don't know which way round yet).

There are two less cats than dogs, so the purple bar must be for cats (because we know how many dogs there are now).

So the orange bar must be for hamsters (because all the rest have been matched up, even though we don't know which way round blue and yellow are yet).

There are twice as many fish as hamsters, so the yellow bar must be for fish. So the blue bar must be for gerbils.

There are half the number of gerbils as there are cats- yes, this works!

During lockdown 2020 we received the following from Clemmie who goes to Thomas's London Day Schools.

Well done Clemmie, that solution is very well shown in your work.

Use the two sets of data to find out how many children there are in Classes 5, 6 and 7.

Have a look at all the information Class 5 have collected about themselves. Can you find out whose birthday it is today?

Have a look at this table of how children travel to school. How does it compare with children in your class?