Take into account that for any repeated measurements, the formula of percentage uncertainty is given by the following formula:
[tex]\text{uncertainty}=\frac{half\text{ the range}}{Average\text{ reading}}\cdot100[/tex]Then, for the percentage uncertainty of density. mass and volume, just use the information about half the range and average reading for each magitude (volume, density and mass)
Consider that half the range is one half the subtraction between the maximum and minimum measurement:
[tex]\text{half the range=(max - min)/2}[/tex]