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Question
70 trees were planted by Parth and 90 trees were planted by Pradnya on the occasion of Tree Plantation Week. Out of these; 25 trees were planted by both of them together. How many trees were planted by Parth or Pradnya?
Solution
Let A be the set of trees planted by Parth and B be the set of trees planted by Pradnya.
So, n(A) = 70; n(B) = 90; n(A ∩ B) = 25
n(A ∪ B) =?
Now, n(A ∪ B) = n(A) + n(B) - n(A ∩ B)
n(A ∪ B) = 70 + 90 - 25
n(A ∪ B) = 135
Hence, the number of trees planted by Parth or Pradnya is 135.
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