The number of straight lines that can be formed by joining 20 points no three of which are in the same straight line except 4 of them which are in the same line
A
183
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B
186
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C
197
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D
185
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Solution
The correct option is D185
There are 20 points out of which 4 are in a straight line.
To form a straight line we need 2 points
There are 3 ways
(i) select both points from 1⇒16C2⇒120
(ii) select one from 1 and one from 2
⇒16C1×4C1⇒16×4⇒64
(iii) select both points from 2 in 2 whichever way we select we get