H2 Maths students often make this mistake, practise this
question to learn how to use the correct concept correctly.
Question
A shopper buys two kinds of vegetables in a shop. The mass of
potatoes and the mass of onions are modelled as having independent
normal distributions.
The mass of potatoes has a mean mass of 3 kg and a standard
deviation of 0.2kg. The mass of onions has a mean mass of 1 kg and
a standard deviation of 0.05kg.
The price of potatoes is 50 cents per kilogramme and the price
of onions is $1.20 per kilogramme.
Find the probability that the total cost of the vegetables lies
between $2.50 and $2.80.
(Hint : X1+X2 +X3 = T
BUT T IS NOT THE SAME AS
3X).