Question

For what percentage of time has life existed on earth (round to the nearest whole number).

Answer 1

This is the concept of arithmetic. To calculate the percentage of time life has existed we proceed as follows;
According to history:
The age of earth is 4.6 billion years
the age of life is as it appeared from unicellular is 3.8 billion years.
thus the percentage of the above will be:
3.8/4.6 x 100
=0.82609x100
=82.609%