The average of 12 numbers is 18.5. The average of the first six numbers is 16.8 and that of the last seven numbers is 17.4. If the 6th number is excluded, then what is the average (correct to one decimal place) of the remaining 11 numbers?

20.1

Sum of 12 numbers = 12 × 18.5 = 222

Sum of 1st six numbers = 6 × 16.8 = 100.8

Sum of last seven numbers = 7 × 17.4 = 121.8

6th number = ( 121.8 + 100.8 ) - 222 = 0.6

Excluding 6th number , Sum of 11 numbers = 222 - 0.6 = 221.4

Average of 11 numbers = \(\frac{221.4}{11}\) = 20.1