Question

there are 10 points in a plane and 4 of them are collinear. the no.of straight lines joining any two points is
a) 45
b) 48
c) 40
d) 50
plz answer fast guys
exam time​

Answer 1

oi your answer is (c) 40

explanation:

points when joined in a plane will make 1 line.

If the total number of point is 10, the total number of line = 10C2

But 4 points are collinear, so the lines make with these 4 points are same.

Hence there is 1 common line joining the 4 collinear point.

Finally, the number of straight line = 10C2 - 4C2 + 1 = 45 - 6 + 1 = 40

stayy safe Amii!!

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