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Question
Find the mean of 75 numbers, if the mean of 45 of them is 18 and the mean of the remaining ones is 13.
Solution
Mean of 45 numbers = 18
⇒ Sum of 45 numbers = 18 x 45 = 810
Mean of remaining ( 75 - 45 ) 30 numbers = 13
⇒ Sum of remaining 30 numbers = 13 x 30 = 390
⇒ Sum of all the 75 numbers = 810 + 390 = 1200
⇒ Mean of all the 75 numbers = `1200/75` = 16
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