A researcher in Guyana models the spread of a plant disease using the equation N = 5 × 2ᵗ, where N is the number of infected plants and t is time in weeks. How many plants will be infected after 3 weeks?

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Question

A researcher in Guyana models the spread of a plant disease using the equation N = 5 × 2ᵗ, where N is the number of infected plants and t is time in weeks. How many plants will be infected after 3 weeks?

Accepted Answer

40 — Award 1 mark for correct substitution and calculation: N = 5 × 2³ = 5 × 8 = 40. A is incorrect — this results from 5 × 3 instead of 5 × 2³. B is incorrect — this may result from 5 × 6. D is incorrect — this would be 5 × 2⁴ (after 4 weeks).

Answer

40

Answer

80

Answer

30

Answer

15

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