Question
The average of 30 numbers is 55. The average of the
first 15 numbers is 50 and the average of the last 12 numbers is 55. What is the average of 68, 74 and the remaining 3 numbers?Solution
Sum of all 30 terms = 30 x 55= 1650 Sum of first 15 terms = 15× 50 = 750 Sum of last 12 terms = 12 x 55 = 660 After removing the first 15 and last 12 terms, there will be 3 terms remaining.  Sum of remaining 3 terms = 1650 (750 +660) = 240 According to the question, 68 and 74 are added to the sum of 3 terms. Thus, the number of total terms becomes 5. Average of 5 terms = (240 +68 + 74)/5 382/5= 76.4  76.4 is the average of 68, 74 and the remaining 3 numbers.
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