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How many different straight lines can be formed by joining 12 different points on a plane of which four are collinear and the rest are non collinear?

How many different straight lines can be formed by joining 12 different points on a plane of which four are collinear and the rest are non collinear?

Grade:12th pass

2 Answers

Sourabh Singh IIT Patna
askIITians Faculty 2104 Points
7 years ago
See out of 8 non collinear points I will get 8C2 lines and out of 4 collinear points I will get only 1 line .But from the mix of collinear and no collinear I will get 8C1 *4C1 lines .

I hope this helps.
yash
25 Points
7 years ago
Its is simply 12 C2 – 4C2  + 1 . i will explain you ,so number of ways in which we can select 2 points from 10 points is   12 C2  no you subtract 4Ccombination from this .  but 4C2 can make 6 straight line out of which we will consider one as it is different . volaa  

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