Hi Bobby,

My immediate response is that 50 is very close to zero percent of 4.5 billion.

Suppose the question was "What percent is 50 of 200?" To do this I would calculate the fraction that 50 is of 200, that is $\frac{50}{200} = \frac14 = 0.25.$ To convert the decimal fraction to a percent multiply by 100 and get that 50 is 25% of 200.

To answer your question calculate the decimal fraction that 50 is of 4.5 billion and the multiply by 100 to convert the fraction to a decimal.

Penny