The average of five numbers is 281. The average of the first two numbers is 280 and the average of the last two numbers is 178.5. What is the third number ?
(a) Assume the third number = x
According to question
2 × 280 + x + 178.5 × 2 = 281 × 5
or, 560 + x + 357 = 1405
or, x + 917 = 1405
or, x = 1405 - 917 = 488