Calculate the number of cells in a hummingbird assuming it weighs 10-2 kg

A popular assumption is that the mass of a cell s 10 times the mass of a bacterium, which is about 10⁻¹² g.

Therefore, one cell of the humming bird has a mass of about 10⁻¹¹ g.

The number of cells in a hummingbird weighing 10⁻² g is

10⁻²/10⁻¹¹ = 10⁹

Answer: 10⁹ or a billion.