1.) A man's weight is 122 lb using a bathroom scale. What is his mass in kg using the conversion factor 2.2 lb = 1.0 kg. Find the percentage error in his mass if the standard 1kg is 2.2046 lb.

2.) What are the parts of the human body used in measurement?

3.) A cell membrane is 7.0 nm thick. If there are 7.2 x 106 cell membranes, how thick is the stack?

4.) Assume that a man is mostly made up of water. If the mass of the person is 55 kg and that of the water molecule is 29.9 x 10-27 kg, estimate the number of molecules of the person.