m4maths Maths Puzzle

There are 10 points in a plane out of which 4 are collinear. How many lines can be drawn.

Read Solution (Total 3)

10C2 -4C2+1 = 45-6+1= 40 lines
11 years agoHelpfull: Yes(8) No(1)

40 total lines.

the first line made is by the colinear points, giving you one line.

each of the four colinear points can make a line with the 6 others, giving you

4*6= 24 more lines (25 in total)

then, each of the 6 points can make a line with five other points that are not in the colinear line.

The first of the 6 makes a line with the next five, giving you five lines, the second of the 6 has already made a line with the first when the first drew all of its lines out, so it can only make 4 more lines, the third of the six has already made a line with the first two, it only has three lines it can draw, the pattern continues giving you

5+4+3+2+1= 15 lines

add that to the original 25 made by the colinear points and you get 40 lines in total.
11 years agoHelpfull: Yes(6) No(4)
1+6C2=1+15=16
11 years agoHelpfull: Yes(0) No(2)

m4maths Other Question

lcm of x^3+1, x^2-1, x^3-1 will be

Options 1) (x^2+x+1)(x^2-x+1)
2) (x^4-1)
3) (x^6-1)(x^2+1)
4) (x^6+1)(x^2-1)
5) (x^6-1)
6) (x^6+1)
7) (x^3+x^2+x+1)
8) (x-1)(x^2+1)(x+1)(x^2-1)
9) (x^4+1)
10) none of these k,4,n,40,121,364 is a sequence.Then k+n will be