There is only a glass, water and balance around. How can we measure the density of pebbles? Help me

There is only a glass, water and balance around. How can we measure the density of pebbles? Help me

First, pour the water into the glass, then put in the pebble, and calculate the volume difference between the two times, that is, the volume of the pebble. When measuring the mass of the pebble with the balance, the density can be calculated with the formula

Use a glass, water and balance to measure the density of stones. A glass filled with water has a total mass of M 1 = 200 g
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The total mass of glass, water and stone is M2 = 215g; after taking out the stone, the total mass of water and glass is m3 = 190g, and the stone density is calculated?

After removing the stone, the water is reduced by M1-M3 = 10g, the volume of overflow water is 10ml, the weight of stone is M2-M3 = 25g, the density of stone is 25 △ 10 = 2.5g/cm3

How to measure the density of milk with a glass, water and balance?
(write all the experimental steps and the expression of milk density)

Step 1: weigh the mass of the glass M1 (g) with the balance. Step 2: fill the glass with water and weigh the total mass M2 (g), then the mass of a glass of water is m2-m1 (g). Step 3: fill the glass with milk and weigh the total mass m3 (G), then the mass of a glass of milk is m3-m1 (g). Step 4: calculate the density of milk in step 2