To answer this question, we have that:
An ant weighs about:
[tex]2\cdot10^{-5}lb[/tex]There are about:
[tex]1\cdot10^{15}ants\text{ in our planet}[/tex]Then we need to multiply both values as follows:
[tex]2\cdot10^{-5}\frac{lb}{ant}\cdot1\cdot10^{15}ants[/tex]Now, we can multiply both numbers as follows:
[tex]2\cdot1\cdot(10^{-5}\cdot10^{15}_{})=2\cdot(10^{-5+15_{}})=2\cdot10^{10}[/tex]The units can be managed as follows:
[tex]\frac{lb}{ant}\cdot ant=lb[/tex]In summary, therefore, we finally have that all of the ants on Earth weigh:
[tex]2\cdot10^{10}lb[/tex]