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1.Set Theory
hard
माना $S =\{4,6,9\}$ तथा $T =\{9,10,11, \ldots, 1000\}$ हैं। यदि $A =\left\{ a _1+ a _2+\ldots+ a _{ k }: k \in N , a _1, a _2\right.$, $\left.a_3, \ldots, a_k \in S\right\}$ है, तो समुच्चय $T-A$ में सभी अवयवों का योग है $..........।$
A
$10$
B
$9$
C
$11$
D
$12$
(JEE MAIN-2022)
Solution
$S =\{4,6,9\} \quad T =\{9,10,11 \ldots 1000\}$
$A \left\{ a _{1}+ a _{2}+\ldots . .+ a _{ k }: K \in N \right\} \,and\, a _{ i } \in S$
Here by the definition of set '$A$'
$A=\{a: a=4 x+6 y+9 z\}$
Except the element $11$,every element of set $T$ is of of the form $4 x+6 y+9 z$ for some $x, y, z \in W$
$\therefore T – A =\{11\}$
Standard 11
Mathematics