The average of nine numbers is 60, that of the first five numbers...

Given: Average of nine numbers $=60$ Average of first five numbers $=55$ and average of next three numbers $=65$ Tenth number $=$ Ninth number +10 Concept used: Average $=$ Total sum of all numbers $/$ (Count of the numbers) Calculation: The sum of nine numbers (=60 \times 9=540) The sum of the first five numbers (=55 \times 5=275) The sum of the next three numbers (=65 \times 3=195) Ninth number $=(540-275-195)=(540-470)=70$ (\therefore) Tenth number $=70+10=80$