MEDIUM
CAT
IMPORTANT
Earn 100
There are seven pairs of black shoes and five pairs of white shoes. They are all put in a box and shoes are drawn one at a time. What is the minimum number of shoes required to be drawn out to get at least one correct pair(Black or White shoes) of shoes?
50% studentsanswered this correctly
Important Questions on Permutations and Combinations
EASY
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IMPORTANT
In how many ways, one white and one black rook can be placed on a chessboard so that they are never in an attacking position?
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IMPORTANT
How many -digit numbers have all their digits either all odd or all even?
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How many -digit numbers have at least even digit?
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IMPORTANT
On a triangle ABC, on the side AB, points are marked, points are marked on the side BC and points are marked on the side AC (none of the points being the vertex of the triangle). How many triangles can be made by using these points?
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IMPORTANT
In the Sunita Building in Mumbai, there are floors plus the ground floor. people get into the lift of the building on the ground floor. The lift does not stop on the first floor. If and people alight from the lift on its upward journey, then in how many ways can they do so? (Assume they alight on different floors.)
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IMPORTANT
There are doctors in the surgical department of the AIIMS. In how many ways can they be arranged to form a team with surgeon and assistant.
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IMPORTANT
How many five-digit numbers, which do not contain identical digits, can be written by means of the digits ?
EASY
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IMPORTANT
How many different four-digit numbers can be written using only once such that the number is contained once?
