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Ten points are marked on a straight-line and 11 points are marked on another straight-line. How many triangles can be constructed with vertices from among the above points?

  1. 495
  2. 550
  3. 1045
  4. 2475

Answer

Triangle can be formed by taking any two points of a straight line and third point on the second straight line.

10C2 × 11 + 11C2 × 10 = (45 x 11) + (55 x 10) = 1045

The correct option is C.