Calculate the average of three density measurements of water

Graduated cylinder, adding increments of 10 mL of water to total 30 mL.

1. You have taken measurements of three volumes of water. Record the following masses for each of the three measurements (in grams):

(a) mass of the graduated cylinder alone: 87.470 g

(b) mass of the graduated cylinder plus the water inside: 117.470 g

(c) net mass of the water: 30.000 g

2. For each of the three measurements, record and calculate the following. Note that a cubic centimeter (cm³) is equivalent to a milliliter (mL).

(a) total volume of water (in mL or cm³): 30 mL

(b) total mass of water (in grams): 30.000 g

(c) density of the water (in grams/cm³): 1.00 g/mL

3. Calculate the average of the three density measurements for water.

Part 3, is where I'm having trouble with.

Add up the 3 densities of the water, and divide by 3. The real answer is 1, but yours may be slightly off because of human error.