In 2000, the world population was 6.1 billion. In 2015, the world population was 7.3 billion. Work out the percentage increase in population. Give your answer correct to 1 decimal place.

Astudent draws two parabolas on graph paper. both parabolas cross the x-axis at (–4, 0) and (6, 0). the y-intercept of the first parabola is (0, –12). the y-intercept of the second parabola is (0, –24). what is the positive difference between the a values for the two functions that describe the parabolas? write your answer as a decimal rounded to the nearest tenth