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QJEEM23Made5f: JEE Main 2023 Mathematics - Class 11 JEEM23Made5f Solution: Let S = {1, 2, 3, 5, 7, 10, 11}. The number of non-empty…

Let S = {1, 2, 3, 5, 7, 10, 11}. The number of non-empty subsets of S that have the sum of all elements a multiple of 3, is _____________.

Step-by-Step Verified Solution

Elements of the type 3k=33 \mathrm{k}=3

Elements of the type 3k+1=1,7,93 \mathrm{k}+1=1,7,9

Elements of the type 3k+2=2,5,113 \mathrm{k}+2=2,5,11

Subsets containing one element S1=1S_1=1

Subsets containing two elements

S2=3C1×3C1=9

Subsets containing three elements

S3=3C1×3C1+1+1=11

Subsets containing four elements

S4=3C3+3C3+3C2×3C2=11

Subsets containing five elements

S5=3C2×3C2×1=9

Subsets containing six elements S6=1\mathrm{S}_6=1

Subsets containing seven elements S7=1\mathrm{S}_7=1

⇒ sum =43

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