Combinatorics: Triangles from Points
CAT 1999 Slot 1 · Quantitative Ability · Easy · Permutations and Combinations
This is an easy Quantitative Ability question from the CAT 1999 Slot 1 paper. It tests Permutations and Combinations. The full answer key and a step-by-step explanation are below — try it yourself first, then reveal the solution.
Ten points are marked on a straight line and 11 points are marked on another parallel straight line. How many triangles can be constructed with vertices from among the above points?
- A.
495
- B.
550
- C.
1045
- D.
2475
C
Explanation
A triangle requires 3 vertices. We can either choose 2 points from line 1 and 1 from line 2, or 1 point from line 1 and 2 from line 2: Number of triangles = .
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