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There are 15 points in a plane of which ...

There are 15 points in a plane of which 4 points lie in one stright line and another 5 points lie in another straight line . The two lines are parallel and no three of the remaining 6 points are collinear . Find
(a) the number of straight lines and
(b) the number of trangles that can be formed by joining the 15 points .

Text Solution

Verified by Experts

The correct Answer is:
(a) `.^(15)C_(2)-.^(4)C_(2)-.^(5)C_(2)+2=91`
(b) `.^(15)C_(3)-.^(4)C_(3)-.^(5)C_(3)=441`
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CHHAYA PUBLICATION-PERMUTATION AND COMBINATION -EXERCISE 7B ( Short Answer Type Questions )
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