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IMPORTANT
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Assuming the balls to be identical except for difference in colours, the number of ways in which one or more balls can be selected from white, green and black balls is
(a)
(b)
(c)
(d)

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Important Questions on Permutation and Combination
HARD
JEE Main/Advance
IMPORTANT
Let be the number of all possible triangles formed by joining vertices of an -sided regular polygon. If then the value of is

MEDIUM
JEE Main/Advance
IMPORTANT
The number of integers greater than that can be formed using the digits and without repetition is

HARD
JEE Main/Advance
IMPORTANT
If all the words (with or without meaning) having five letters, formed using the letters of the word and arranged as in a dictionary; then the position of the word is

HARD
JEE Main/Advance
IMPORTANT
A man has friends, of them are ladies and are men. His wife also has friends, of them are ladies and are men. Assume and have no common friends. Then, the total number of ways in which and together can throw a party inviting ladies and men, so that friends of each of and are in this party, is

MEDIUM
JEE Main/Advance
IMPORTANT
From different novels and different dictionaries, novels and dictionary are to be selected and arranged in a row on a shelf so that the dictionary is always in the middle. The number of such arrangements is

HARD
JEE Main/Advance
IMPORTANT
Let be the set of all triangles in the - plane, each having one vertex at the origin and the other two vertices lie on coordinate axes with integral coordinates. If each triangle in has area sq. units, then the number of elements in the set is

MEDIUM
JEE Main/Advance
IMPORTANT
Consider three boxes, each containing balls labelled Suppose one ball is randomly drawn from each of the boxes. Denote by the label of the ball drawn from the th box, Then, the number of ways in which the balls can be chosen such that is

HARD
JEE Main/Advance
IMPORTANT
How many positive integers are there such that is a divisor of one of the numbers
