The average of ten numbers is 18.2. The average of the first four numbers is 16.6 and that of the last seven numbers is 20.8. If the 4th number is excluded, then the average of the remaining numbers is (correct to one decimal place):

Sum of 10 numbers = 18.2 × 10 = 182. Sum of first 4 numbers = 16.6 × 4 = 66.4. Sum of last 7 numbers = 20.8 × 7 = 145.6. The 4th number is counted in both groups, so: Sum of all 10 + 4th number = 66.4 + 145.6 = 212. Therefore, 4th number = 212 - 182 = 30. Sum of remaining 9 numbers (excluding 4th) = 182 - 30 = 152. Average of remaining 9 numbers = 152/9 = 16.89 ≈ 16.9.