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

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