Answer:
18.7 years
Step-by-step explanation:
This is a compound interest problem and the following variables have been given;
Principal = 4000; this is the amount o be invested
APR = 9%; this is the compound interest to be earned
Accumulated amount = 20,000
We are required to determine the duration in years. We apply the compound interest formula;


The next step is to introduce natural logarithms in order to determine n;

The number of years required is thus 18.7 years
Answer:
The number of cases prior to the increase is 50.
Step-by-step explanation:
It is given that the number of measles cases increased by 13.6% and the number of cases after increase is 57.
We need to find the number of cases prior to the increase.
Let x be the number of cases prior to the increase.
x + 13.6% of x = 57



Divide both the sides by 1.136.



Therefore the number of cases prior to the increase is 50.