There are 10 points in a plane, of which exactly 4 lie on one straight line and no other three are in a line. How many different straight lines can be drawn through pairs of these points?

Question

Accepted Answer

40. All pairs: ^10C_2=45. The 4 collinear points give ^4C_2=6 pairs but only 1 line. Lines = 45-6+1=40.

There are 10 points in a plane, of which exactly 4 lie on one straight line and no other three are in a line. How many different straight lines can be drawn through pairs of these points?

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