JEE Main 2020 — Sets And Relations Question with Solution
From: JEE Main 2020 (Online) 4th September Evening Slot
Question
Let where each Xi contains 10 elements and each Yi contains 5 elements. If each element of the set T is an element of exactly 20 of sets Xi’s and exactly 6 of sets Yi’s, then n is equal to :
Choose an option
Show full solutionCorrect option: A
Correct answer
A30
Step-by-step explanation
X1, X2,....., X50 = 50 sets. Given each sets having 10 elements.
So total elements = 50 10
\times {{50 \times 10} \over {20}}{{50 \times 10} \over {20}} \therefore {{50 \times 10} \over {20}}{{5 \times n} \over {20}} \Rightarrow $$ n = 30
So total elements = 50 10
\times {{50 \times 10} \over {20}}{{50 \times 10} \over {20}} \therefore {{50 \times 10} \over {20}}{{5 \times n} \over {20}} \Rightarrow $$ n = 30
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