The average of 9 numbers is 34. If the average of the first 4 numbers is 38 and that of the last 4 is 35, then find the 4th number

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1. Answer:

   The average of 9 numbers is 40 . If the average of first five numbers is 38 and that of the last five numbers is 50,then what is the fifth number?

   (1) Avg of 9 numbers = 40. So total of 9 numbers = 9 * 40 = 360.

   (2) Avg of first 5 is 38. Total of first 5 is = 5 * 38 = 190.

   (3) Avg of last 5 is 50. Total of last 5 is = 5 * 50 = 250.

   (4) Total of first 5 plus last 5 = 190 + 250 = 440.

   (5) Total of first 4 plus fifth + Total of last 4 plus fifth = 440

   (6) Total of all 9 numbers + fifth number = 440.

   (7) 360 + fifth number = 440.

   (8) Fifth number = 440 – 360 = 80.

   Answer: Fifth Number = 80.

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