Volume plays an important role in the problems. The formula
D = M/ V (density equals mass divided by volume)
Also can be written as M = D x V (mass equals density times volume)
When two things have the same mass, their volume determines the density – or in your problems, how easily you can lift something. The higher the density, the harder it is to lift the object.
Even though the mass of the cylinder is much less than the mass of the girl, the cylinder’s volume is also much less. The girl’s has a large mass but her volume is also very large. For example, the height of the cylinder is probably 10 or 12 inches tall. The girl is at least 60 inches tall. Therefore, the density of the cylinder is higher and that’s why it’s more difficult to lift it.