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There are 10 points in a plan, out of which 5 are collinear. Find the number of straight lines formed by joining them.

36
45
30
35

Correct Answer: 36

Explanation:

Required number of straight lines
=ⁿC₂ - ^mC₂ + 1
Here, n = 10, m = 5
= ¹⁰C₂ - ⁵C₂ + 1
= 45 - 10 + 1 = 36

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