We can get the triangles in two different ways taking two points from the line having 10 points (in 10C2 ways i.e. 45 ways) and one point from the line consisting of 11 points (in 11 ways). So, the number of triangle =45×11=495 Now, taking two points from the line having 11 points (in 11C2, i.e. 55 ways) and one point from the line consisting of 10 points (in 10 ways), the number of triangle here is 55×10=550 Hence, required number of triangle=495+550 =1045