A hollow copper ball has a mass of 178g and a volume of 50 cubic centimeters. What is the volume of the hollow part of the ball, The format is easy to understand

A hollow copper ball has a mass of 178g and a volume of 50 cubic centimeters. What is the volume of the hollow part of the ball, The format is easy to understand

50-178÷7.9
=50-20
=30 cm3
The volume of the hollow part of the ball is 30 cubic centimeters

The volume of the copper ball is 6 cubic centimeters and its mass is 26.7 grams. Is the copper ball solid or hollow? If it is hollow, what is the volume of the hollow part?
Urgent! Heroes help! Thank you

It is known that M = 26.7g, the density of copper = 8.9g/cm3
Find v
V = mass divided by density = 26.7g/8.9gcm3 = 3cm3
Because 6cm3 ＜ 3cm3
So the copper ball is hollow, the hollow part = 6-3 = 3cm3

The volume of the hollow copper ball with a mass of 178g is 35cm3. After the hollow part is filled with a certain liquid, the mass becomes 190g, and the solution is obtained
The volume of the hollow copper ball with a mass of 178g is 35cm3. When the hollow part is filled with a certain liquid, the mass becomes 190g, and the density of the injected liquid is calculated.

The density of copper is known as P = 8.9g/cm & sup3;
35cm & sup 3; the material grain should be 35p = 311.5g
Now we have 178g left
133.5g less
That is, 15 cm & sup 3 less;
The liquid mass is 190-178 = 12g
So the liquid density is 12 / 15 = 0.8g/cm & sup3;