2025 TGM P2 Q9

2025 TGM P2 Q9

10 marks

In this question, you should state clearly the values of the parameters of any normal distribution you use.
A supermarket sells two types of durians, D\(26\) and Civet King. The durians are sold by weight. The masses, in kilograms, of D\(26\) and Civet King are modelled as having normal distributions. The means and standard deviations of these distributions, and the selling prices, in \(\$\) per kilogram, are shown in the following table.

Mean (kg)Standard Deviation (kg)Selling price (\(\$\) per kg)
D26\(1.8\)\(0.02\)\(9\)
Civet King\(\mu\)\(\sigma\)\(18\)
  1. Find the probability that the mass of a randomly selected D\(26\) is less than \(1.76\text{ kg}\).

    [2]
  2. It is known that \(65\%\) of the Civet King have a price greater than \(\$32.16\) and \(25\%\) of them have a price less than \(\$31.98\). Show that \(\mu = 1.8\) and \(\sigma = 0.035\), correct to \(2\) significant figures.[3]
  3. A customer buys \(4\) D\(26\) durians and \(3\) Civet King durians. Find the probability that the total cost of his purchase is more than \(\$160\).

    [4]
  4. State an assumption needed for your calculations in part (iii).

    [1]
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