Most plants of a certain type have three leaves. However, it is known that, on average, 1 in 10000 of these plants have four leaves, and plants with four leaves are called 'lucky'. The number of lucky plants in a random sample of 25000 plants is denoted by $$\(X\)$$. The number of lucky plants in a random sample of $$\(n\)$$ plants, where $$\(n\)$$ is large, is denoted by $$\(Y\)$$. Given that $$\(\mathrm{P}(Y \geqslant 1)=0.963\)$$, correct to 3 significant figures, use a suitable approximating distribution to find the value of $$\(n\)$$. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics
IGCSE&ALevel
CAIE
Exam No:9709_s21_qp_63 Year:2021 Question No:5(d)

Answer:

\(1-\mathrm{e}^{-\lambda}=0.963\)
\(\lambda=-\ln 0.037(=3.2968\) or \(3.30\) or \(3.3)\)
\(n=33000(3 \mathrm{sf})\)

Knowledge points:

6.1.1 use formulae to calculate probabilities for the distribution $\text { Po }(\lambda)$

Solution:

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