The US population in millions is Pt today where time t is me

The US population in millions is P(t) today, where time t is measured in years. For each statement, choose one of the expression A-H that represents it.

Solution

P(t) is in millions

1) The population after 100,000 people have emigrated

==> Population is decreased by 100,000 = 0.1 million people

==> P(t) - 0.1 (Option D)

2) Ten percent of the population we have today

==> (10/100) P(t) = 0.1 P(t) (Option G)

3) Todays population plus 10 million immigrants = P(t) + 10 (Option H)

4) The population 10 years before today = P(t - 10) [ Option A]