The question does not contain sufficient information for an accurate answer. I assume this has to do with measurements and uncertainty.
Measurements of the volume of the cylinder are made thrice and the values obtained are V1, V2 and V3.
To find the average volume of the cylinder, the three values are added and the result divided by 3. The average volume here will be: (V1 + V2 + V3)/3
It is important to keep in mind the accuracy of measurements made. The accuracy of the final result cannot be greater than that of the least accurate measurement. For example if V1 = 20.50 mL, V2 = 21 mL and V3 = 21.5 mL, the average volume would be 21 mL. It would be incorrect to state that the average volume is 21.00 mL or 21.0 mL as the least accurate reading is 21 mL.