The probability that a specific variety of tomato seed fails to germinate is 0.06. A gardener plants several trays of these seeds.
Find the probability that
a tray containing 25 seeds has exactly 2 seeds that fail to germinate.
a larger batch of 100 seeds has more than 8 seeds that fail to germinate.
A commercial greenhouse plants a large shipment of 800 seeds.
Using a suitable approximation, find the probability that the greenhouse's shipment will contain less than 40 seeds that fail to germinate.
390 exam-style questions on OCR A Level Maths 2.4 Statistical Distributions, covering 2.4.1 Discrete probability distributions, 2.4.2 Binomial distribution as a model, 2.4.3 Calculating binomial probabilities, 2.4.4 Mean and variance of the binomial (A-level only), 2.4.5 Normal distribution as a model (A-level only), 2.4.6 Probabilities using the normal distribution (A-level only), 2.4.7 Links to histograms, mean and standard deviation (A-level only), and 2.4.8 Selecting an appropriate distribution (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.