Question
The average of 13 natural numbers is 45. If the average
of first 7 numbers is 35 and the average of last seven numbers is 55, then find the value of number which is at 7 th  place.Solution
Sum of the 13 natural numbers = 13 x 45 = 585
Sum of the first 7 numbers = 7 x 35 = 245
Sum of the last 7 numbers = 7 x 55 = 385
Therefore, required number = {(245 + 385) - 585} = 45
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