Probability Store Problem

[ruby_duby]

Hi i need help on the following question:

In a teashop 70% of customers order tea with milk, 20% tea with lemon and 10% with neither. of those taking tea with milk 3/5 take sugar, of those taking tea with lemon 1/4 take sugar, and of those taking tea with neither milk or lemon 11/20 take sugar. a customer is then chosem at random.

i need to find the probability that the customers take suggar or milk or both. i know that the answer is o.525 but i don't know how.

can anybody help me please?

 

[radou]

i need to find the probability that the customers take suggar or milk or both. [/COLOR]

Hint: the word 'or' is interpreted as the operation '+' while calculating probabilities.

 

[ruby_duby]

yes i understand that
but does that mean that i do

(0.7x3/5) + 0.7 + 3/5 + 1/4 + 11/20
if this is the case then it doesn't equal 0.525

 

[radou]

yes i understand that
but does that mean that i do

(0.7x3/5) + 0.7 + 3/5 + 1/4 + 11/20
if this is the case then it doesn't equal 0.525

Not only it doesn't equal 0.525 , but it is greater than 1, which cannot be. Just to make sure, the question is: 'Calculate the probability that the person chosen takes (sugar OR milk) OR (sugar AND milk)'? The case (sugar OR milk) would not make sence, because every one is taking sugar.

 

[ruby_duby]

i can't really make sense of the question either, but i think it means (sugar and milk) or (sugar or milk)