LFM Stats And Pure

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Let $A$ and $B$ be two sets containing four and two elements respectively. Then the number of subsets of the set $A \times B$, each having at least three elements is
(1) 510
(2) 219
(3) 256
(4) 275
If 12 identical balls are to be placed in 3 identical boxes, then the probability that one of the boxes contains exactly 3 balls is
(1) $22 \left( \frac { 1 } { 3 } \right) ^ { 11 }$
(2) $\frac { 5 } { 19 }$
(3) $55 \left( \frac { 2 } { 3 } \right) ^ { 10 }$
(4) $220 \left( \frac { 1 } { 3 } \right) ^ { 12 }$
jee-main 2016 Q63 Basic Combination Computation View
If $\frac { { } ^ { n + 2 } C _ { 6 } } { { } ^ { n - 2 } P _ { 2 } } = 11$, then $n$ satisfies the equation:
(1) $n ^ { 2 } + n - 110 = 0$
(2) $n ^ { 2 } + 2 n - 80 = 0$
(3) $n ^ { 2 } + 3 n - 108 = 0$
(4) $n ^ { 2 } + 5 n - 84 = 0$
A man $X$ has 7 friends, 4 of them are ladies and 3 are men. His wife $Y$ also has 7 friends, 3 of them are ladies and 4 are men. Assume $X$ and $Y$ have no common friends. Then the total number of ways in which $X$ and $Y$ together can throw a party inviting 3 ladies and 3 men, so that 3 friends of each of $X$ and $Y$ are in this party is:
(1) 485
(2) 468
(3) 469
(4) 484
$n$ - digit numbers are formed using only three digits 2,5 and 7 . The smallest value of $n$ for which 900 such distinct numbers can be formed, is
(1) 6
(2) 8
(3) 9
(4) 7
Let $S = \{ 1,2,3 , \ldots , 100 \}$, then number of non-empty subsets $A$ of $S$ such that the product of elements in $A$ is even is :
(1) $2 ^ { 100 } - 1$
(2) $2 ^ { 50 } + 1$
(3) $2 ^ { 50 } \left( 2 ^ { 50 } - 1 \right)$
(4) $2 ^ { 50 } - 1$
A group of students comprises of 5 boys and n girls. If the number of ways, in which a team of 3 students can randomly be selected from this group such that there is at least one boy and at least one girl in each team, is 1750, then n is equal to
(1) 24
(2) 27
(3) 25
(4) 28
A committee of 11 member is to be formed from 8 males and 5 females. If $m$ is the number of ways the committee is formed with at least 6 males and $n$ is the number of ways the committee is formed with at least 3 females, then:
(1) $m = n = 68$
(2) $n = m - 8$
(3) $m = n = 78$
(4) $m + n = 68$
jee-main 2019 Q64 Basic Combination Computation View
Consider three boxes, each containing 10 balls labelled $1,2 , \ldots , 10$. Suppose one ball is randomly drawn from each of the boxes. Denote by $n _ { i }$, the label of the ball drawn from the $i ^ { \text {th } }$ box, $( i = 1,2,3 )$. Then, the number of ways in which the balls can be chosen such that $n _ { 1 } < n _ { 2 } < n _ { 3 }$ is:
(1) 240
(2) 82
(3) 120
(4) 164
jee-main 2019 Q69 Geometric Combinatorics View
Let $S$ be the set of all triangles in the $xy$-plane, each having one vertex at the origin and the other two vertices lie on coordinate axes with integral coordinates. If each triangle in $S$ has area 50 sq. units, then the number of elements in the set $S$ is:
(1) 36
(2) 32
(3) 9
(4) 18
jee-main 2020 Q53 Geometric Combinatorics View
Let $n > 2$ be an integer. Suppose that there are $n$ Metro stations in a city located around a circular path. Each pair of the nearest stations is connected by a straight track only. Further, each pair of the nearest station is connected by blue line, whereas all remaining pairs of stations are connected by red line. If number of red lines is 99 times the number of blue lines, then the value of $n$ is
(1) 201
(2) 200
(3) 101
(4) 199
There are 3 sections in a question paper and each section contains 5 questions. A candidate has to answer a total of 5 questions, choosing at least one question from each section. Then the number of ways, in which the candidate can choose the questions, is:
(1) 3000
(2) 1500
(3) 2255
(4) 2250
jee-main 2020 Q53 Basic Combination Computation View
If $a , b$ and $c$ are the greatest values of ${}^{ 19 } C _ { p } , {}^{ 20 } C _ { q }$ and ${}^{ 21 } C _ { r }$ respectively, then:
(1) $\frac { a } { 11 } = \frac { b } { 22 } = \frac { c } { 21 }$
(2) $\frac { a } { 10 } = \frac { b } { 20 } = \frac { c } { 21 }$
(3) $\frac { a } { 11 } = \frac { b } { 22 } = \frac { c } { 42 }$
(4) $\frac { a } { 10 } = \frac { b } { 11 } = \frac { c } { 42 }$
The value of $\sum _ { r = 0 } ^ { 20 } { } ^ { 50 - r } C _ { 6 }$ is equal to:
(1) ${ } ^ { 51 } C _ { 7 } - { } ^ { 30 } C _ { 7 }$
(2) ${ } ^ { 50 } C _ { 7 } - { } ^ { 30 } C _ { 7 }$
(3) ${ } ^ { 50 } C _ { 6 } - { } ^ { 30 } C _ { 6 }$
(4) ${ } ^ { 51 } C _ { 7 } + { } ^ { 30 } C _ { 7 }$
jee-main 2020 Q56 Basic Combination Computation View
The number of ordered pairs $( r , k )$ for which $6 . { } ^ { 35 } C _ { r } = \left( k ^ { 2 } - 3 \right) . { } ^ { 36 } C _ { r + 1 }$, where $k$ is an integer is
(1) 3
(2) 2
(3) 6
(4) 4
Let $\cup _ { i = 1 } ^ { 50 } X _ { i } = \cup _ { i = 1 } ^ { n } Y _ { i } = T$, where each $X _ { i }$ contains 10 elements and each $Y _ { i }$ contains 5 elements. If each element of the set $T$ is an element of exactly 20 of sets $X _ { i }$'s and exactly 6 of sets $Y _ { i }$'s then $n$ is equal to:
(1) 15
(2) 50
(3) 45
(4) 30
A test consists of 6 multiple choice questions, each having 4 alternative answers of which only one is correct. The number of ways, in which a candidate answers all six questions such that exactly four of the answers are correct, is $\_\_\_\_$
The number of words, with or without meaning, that can be formed by taking 4 letters at a time from the letters of the word 'SYLLABUS' such that two letters are distinct and two letters are alike, is
If $n \geqslant 2$ is a positive integer, then the sum of the series ${ } ^ { n + 1 } C _ { 2 } + 2 \left( { } ^ { 2 } C _ { 2 } + { } ^ { 3 } C _ { 2 } + { } ^ { 4 } C _ { 2 } + \ldots + { } ^ { n } C _ { 2 } \right)$ is
(1) $\frac { n ( n - 1 ) ( 2 n + 1 ) } { 6 }$
(2) $\frac { n ( n + 1 ) ( 2 n + 1 ) } { 6 }$
(3) $\frac { n ( n + 1 ) ^ { 2 } ( n + 2 ) } { 12 }$
(4) $\frac { n ( 2 n + 1 ) ( 3 n + 1 ) } { 6 }$
A scientific committee is to be formed from 6 Indians and 8 foreigners, which includes at least 2 Indians and double the number of foreigners as Indians. Then the number of ways, the committee can be formed, is:
(1) 1050
(2) 1625
(3) 575
(4) 560
jee-main 2021 Q62 Geometric Combinatorics View
Consider a rectangle $ABCD$ having $5,6,7,9$ points in the interior of the line segments $AB , BC , CD , DA$ respectively. Let $\alpha$ be the number of triangles having these points from different sides as vertices and $\beta$ be the number of quadrilaterals having these points from different sides as vertices. Then $(\beta - \alpha)$ is equal to
(1) 795
(2) 1173
(3) 1890
(4) 717
jee-main 2021 Q62 Geometric Combinatorics View
Let $P _ { 1 } , \quad P _ { 2 } \ldots , \quad P _ { 15 }$ be 15 points on a circle. The number of distinct triangles formed by points $P _ { i } , \quad P _ { j } , \quad P _ { k }$ such that $i + j + k \neq 15$, is :
(1) 455
(2) 419
(3) 12
(4) 443
jee-main 2021 Q62 Geometric Combinatorics View
If the sides $A B , B C$ and $C A$ of a triangle $A B C$ have 3,5 and 6 interior points respectively, then the total number of triangles that can be constructed using these points as vertices, is equal to:
(1) 364
(2) 240
(3) 333
(4) 360
If ${ } ^ { n } P _ { r } = { } ^ { n } P _ { r + 1 }$ and ${ } ^ { n } C _ { r } = { } ^ { n } C _ { r - 1 }$, then the value of $r$ is equal to:
(1) 1
(2) 4
(3) 2
(4) 3
Let $Z$ be the set of all integers, $A = \left\{ ( x , y ) \in Z \times Z : ( x - 2 ) ^ { 2 } + y ^ { 2 } \leq 4 \right\}$ $B = \left\{ ( x , y ) \in Z \times Z : x ^ { 2 } + y ^ { 2 } \leq 4 \right\}$ and $C = \left\{ ( x , y ) \in Z \times Z : ( x - 2 ) ^ { 2 } + ( y - 2 ) ^ { 2 } \leq 4 \right\}$ If the total number of relations from $A \cap B$ to $A \cap C$ is $2 ^ { p }$, then the value of $p$ is: (1) 25 (2) 9 (3) 16 (4) 49