the number of straight lines that can be dranw out of 10 points of which 7 are collinear pls explain

10C2-7C2+1 = 45 -21+1= 25
12 years agoHelpfull: Yes(3) No(0)
answer: 45
12 years agoHelpfull: Yes(0) No(3)
the options available are
24 , 23 , 25 , 21
12 years agoHelpfull: Yes(0) No(1)
i think answer is 25...
7c1 x 3c1 = 21...and the 7 collinear points forms 1 straight line...so 21+1=22 and we have 3 points which are not collinear.. so 3c2 = 3...so answer is
22+3=25....
12 years agoHelpfull: Yes(0) No(1)
10 lines can be drawn, as the points are 10
coz every line has a single point.
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straight line can be formed by joining 2 points

so number of ways in which we can select 2 points from 10 points is = 10C2

but it also include that in which 4 points are in straight line . from those 4 points only one line can be formed .

so we have to subtract 4C2 -1 from above result

so total lines are = 10C2 - 4C2 + 1
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the number of straight lines that can be dranw out of 10 points of which 7 are collinear?

pls explain the answers for all these questions..