sandman wrote:
From 4 oranges, 3 bananas and 2 apples, how many selections of 5 pieces of fruit can be made, talking at least one of each kind.
Please post a screenshot of the exact question. I am not sure whether the fruits are to be taken as identical or distinct e.g. whether the 4 oranges are identical or distinct. If nothing is given, I would be tempted to take them as identical.
In that case, I would split 5 into 3 groups with at least one each in the following ways:
{3, 1, 1} - 2 ways (3 oranges or 3 bananas)
{2, 2, 1} - 3 ways (1 orange or 1 banana or 1 apple)
So 5 ways.
But if the fruit pieces are distinct, then we have 9 distinct pieces of which we have to select 5 in 9C5 ways.
Out of these 9C5 ways, you are not allowed those in which one type of fruit is not taken.
No of ways in which oranges are not taken = 5C5
No of ways in which bananas are not taken = 6C5
No of ways in which apples are not taken = 7C5
So total acceptable ways = 9C5 - 5C5 - 6C5 - 7C5 = 126 - 1 - 6 - 21 = 98
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Karishma
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