Out of thirty point in plane, eight of them are collinear. The number of straight lines that can be formed by joining these points is

296

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540

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408

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348

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Solution

The correct option is A $408$
As there are $8$ collinear points, by joining these $8$ points will form one straight line.
Then, the number of straight lines will be
$=^{30} C_{2} -^{8} C_{2} + 1$
$= \frac{30 \times 29}{2} - \frac{56}{2} + 1$
$= 15 (30 - 1) - 28 + 1$
$= 450 - 15 - 28 + 1$
$= 450 - 43 + 1$
$= 407 + 1$
$= 408$

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Out of thirty point in plane, eight of them are collinear. The number of straight lines that can be formed by joining these points is

The correct option is A 408As there are 8 collinear points, by joining these 8 points will form one straight line.Then, the number of straight lines will be =30C2−8C2+1=30×292−562+1=15(30−1)−28+1=450−15−28+1=450−43+1=407+1=408