List of top Mathematics Questions on Combinatorics asked in JEE Main

The number of non-negative integer solutions of the equation \[ a + b + 2c = 22 \] is:

All the words (with or without meaning) formed using all the five letters of the word GOING are arranged as in a dictionary. Then the word OGGIN occurs at the place which is:

The number of ways, in which the letters A, B, C, D, E can be placed in the 8 boxes of the figure below so that no row remains empty and at most one letter can be placed in a box, is:

Let $ p $ be the number of all triangles that can be formed by joining the vertices of a regular polygon $ P $ of $ n $ sides, and $ q $ be the number of all quadrilaterals that can be formed by joining the vertices of $ P $. If $ p + q = 126 $, then the eccentricity of the ellipse $ \frac{x^2}{16} + \frac{y^2}{n} = 1 $ is:

Line L1 of slope 2 and line L2 of slope \( \frac{1}{2} \) intersect at the origin O. In the first quadrant, \( P_1, P_2, ..., P_{12} \) are 12 points on line L1 and \( Q_1, Q_2, ..., Q_9 \) are 9 points on line L2. Then the total number of triangles that can be formed having vertices at three of the 22 points O, \( P_1, P_2, ..., P_{12} \), \( Q_1, Q_2, ..., Q_9 \), is:

For $ n \geq 2 $, let $ S_n $ denote the set of all subsets of $ \{1, 2, 3, \ldots, n\} $ with no two consecutive numbers. For example, $ \{1, 3, 5\} \in S_6 $, but $ \{1, 2, 4\} \notin S_6 $. Then, find $ n(S_5) $.

If \[ \sum_{r=1}^{30} r^2 \left( \binom{30}{r} \right)^2 = \alpha \times 2^{29}, \] then \( \alpha \) is equal to _________.

Let \(M\) be any \(3\times3\) matrix with entries from the set {0, 1, 2}. The maximum number of such matrices, for which the sum of diagonal elements of \(M^T M\) is seven, is __________.

The students S1, S2, ......., S10 are to be divided into 3 groups A, B and C such that each group has at least one student and the group C has at most 3 students. Then the total number of possibilities of forming such groups is _________