Capture Recapture worksheet
10 GCSE practice questions with answers, free to print. Every sheet is generated, so you can make a fresh one whenever you need it.
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3 marks
Amara wants to estimate how many trout there are in the reservoir.
She catches 198 trout, tags them and puts them back.
A week later she catches 77 trout. Of these, 11 are tagged.
Use Amara's results to estimate the number of trout in the reservoir.
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4 marks
Reuben is estimating the number of ladybirds in the hedgerow.
He catches 54 ladybirds, marks them and releases them.
Later that month he catches 78 ladybirds, of which 6 are marked.
(a)Use Reuben's results to estimate the number of ladybirds in the hedgerow.
(b)Write down one assumption you have made.
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3 marks
There are thought to be about 280 carp in the lake. 40 of them are tagged.
Joel catches a sample of 56 carp.
Estimate how many of his sample are tagged.
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4 marks
Priya catches 39 woodlice in the log pile, marks them and puts them back.
(a)A month later she catches 30 woodlice from the log pile. 3 of them are marked.
Estimate the number of woodlice in the log pile.
(b)What percentage of that estimate had been marked?
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3 marks
Amara is estimating the number of frogs in a pond.
She catches some frogs, marked all of them, and returns them to a pond.
Later she catches \(20\) frogs. \(5\) of them are marked.
Using these results, she estimates that there are \(200\) frogs in a pond.
(a)Work out how many frogs she marked the first time.
(b)State one assumption that has been made.
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3 marks
Hafsa wants to estimate how many frogs there are in the pond.
She catches 180 frogs, tags them and puts them back.
A week later she catches 72 frogs. Of these, 9 are tagged.
Use Hafsa's results to estimate the number of frogs in the pond.
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4 marks
Callum is estimating the number of newts in the pond.
He catches 60 newts, marks them and releases them.
Later that month he catches 54 newts, of which 6 are marked.
(a)Use Callum's results to estimate the number of newts in the pond.
(b)Write down one assumption you have made.
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3 marks
There are thought to be about 616 frogs in the pond. 88 of them are tagged.
Aisha catches a sample of 77 frogs.
Estimate how many of her sample are tagged.
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4 marks
Hafsa catches 40 sparrows in the reserve, rings them and puts them back.
(a)A month later she catches 200 sparrows from the reserve. 8 of them are ringed.
Estimate the number of sparrows in the reserve.
(b)What percentage of that estimate had been ringed?
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3 marks
Callum is estimating the number of snails in a garden.
He catches some snails, marked all of them, and returns them to a garden.
Later he catches \(90\) snails. \(4\) of them are marked.
Using these results, he estimates that there are \(450\) snails in a garden.
(a)Calculate how many snails he marked the first time.
(b)State one assumption that has been made.
Answers
- \(1386\)
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(a) \(702\)
(b) e.g. no ladybirds entered or left the hedgerow between the two samples - \(8\)
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(a) \(390\)
(b) \(10\%\) -
(a) \(50\ \text{frogs}\)
(b) The marked frogs had mixed evenly back into the population before the second catch - \(1440\)
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(a) \(540\)
(b) e.g. no newts entered or left the pond between the two samples - \(11\)
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(a) \(1000\)
(b) \(4\%\) -
(a) \(20\ \text{snails}\)
(b) The marked snails had mixed evenly back into the population before the second catch