You already have figured the main idea. In this case, the population is growing 1.9% a year. This word can be translated into: multiplied by 101.9% (100+1.9%). That means the P0 is 6 bill, the base is 101.9%(or 1.019) and the time is 50 years. The calculation would be: <span>P(t)=P₀a^t </span>P(t)=6 billion * 101.9%^50= 6 billion * <span>2.56276= 15.38 billion</span><span>
If one foot in real is 1/2 inches, then 1 inch in a blueprint is 2 feet. So a rectangle 18 by 22 inches will represent 18 * 2 by 22 * 2 feet in real. So the size of the yard is 36 by 44 feet.
