Question

The average of 12 numbers is 18.5. The average of first six numbers is 16.8 and that of the last seven

numbers is 17.4. If the number is excluded, then whatis the average (correct to one decimal place) of

remaining 11 numbers?
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Answer 1

Sum of 6 numbers =60×30=180

Sum of first 4 numbers =4×25=100

Sum of last 3 numbers =3×35=105

∴ Fourth number =(100+105)−180

=205−180

=25