Numerical answer
The average of 11 numbers is 42. The average of the first 6 of these numbers (in the order given) is 38, and the average of the last 6 numbers is 47. Find the 6th number.
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Answer: 48
Sum of all 11 numbers = 11×42 = 462. Sum of first 6 = 6×38 = 228. Sum of last 6 = 6×47 = 282. The 6th number is counted in both the 'first 6' and 'last 6' groups, so: sum(first 6) + sum(last 6) − sum(all 11) = 6th number = 228+282−462 = 48.
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