1
WB JEE 2017
MCQ (Single Correct Answer)
+1
-0.25
Change Language
Out of 7 consonants and 4 vowels, words are formed each having 3 consonants and 2 vowels. The number of such words that can be formed is
A
210
B
25200
C
2520
D
302400
2
WB JEE 2017
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let $$A = \left( {\matrix{ 1 & 1 & 1 \cr 0 & 1 & 1 \cr 0 & 0 & 1 \cr } } \right)$$. Then, for positive integer n, An is
A
$$\left( {\matrix{ 1 & n & {{n^2}} \cr 0 & {{n^2}} & n \cr 0 & 0 & n \cr } } \right)$$
B
$$\left( {\matrix{ 1 & 1 & {n\left( {{{n + 1} \over 2}} \right)} \cr 0 & 1 & n \cr 0 & 0 & 1 \cr } } \right)$$
C
$$\left( {\matrix{ 1 & {{n^2}} & n \cr 0 & n & {{n^2}} \cr 0 & 0 & {{n^2}} \cr } } \right)$$
D
$$\left( {\matrix{ 1 & n & {2n - 1} \cr 0 & {{{n + 1} \over 2}} & {{n^2}} \cr 0 & 0 & {{{n + 1} \over 2}} \cr } } \right)$$
3
WB JEE 2017
MCQ (Single Correct Answer)
+2
-0.5
Change Language
Let a, b, c be such that b(a + c) $$ \ne $$ 0. If $$\left| {\matrix{ a & {a + 1} & {a - 1} \cr { - b} & {b + 1} & {b - 1} \cr c & {c - 1} & {c + 1} \cr } } \right| + \left| {\matrix{ {a + 1} & {b + 1} & {c - 1} \cr {a - 1} & {b - 1} & {c + 1} \cr {{{( - 1)}^{n + 2}}a} & {{{( - 1)}^{n + 1}}b} & {{{( - 1)}^n}c} \cr } } \right| = 0$$, then the value of n is
A
any integer
B
zero
C
any even integer
D
any odd integer
4
WB JEE 2017
MCQ (Single Correct Answer)
+2
-0.5
Change Language
On set A = {1, 2, 3}, relations R and S are given by

R = {(1, 1), (2, 2), (3, 3), (1, 2), (2, 1)},

S = {(1, 1), (2, 2), (3, 3), (1, 3), (3, 1)}. Then,
A
R $$ \cup $$ S is an equivalence relation
B
R $$ \cup $$ S is reflexive and transitive but not symmetric
C
R $$ \cup $$ S is reflexive and symmetric but not transitive
D
R $$ \cup $$ S is symmetric and transitive but not reflexive
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