Final answer:
The formula relating the number of fish to the time is y = 810 * e^((1/11) * ln(972/810) * t). Plugging in t = 21 will give you the number of fish after 21 years.
Step-by-step explanation:
To write a formula relating the number of fish, y, to the time, t, we can use the exponential growth model which is given by the formula: y = A * e^(kt), where A is the initial population and k is the growth rate. In this case, the initial population is 810 fish and the number of fish after 11 years is 972. Plugging these values into the formula, we get: 972 = 810 * e^(11k). To find the value of k, we need to solve this equation for k:
972/810 = e^(11k)
e^(11k) = 972/810
11k = ln(972/810)
k = (1/11) * ln(972/810)
So the formula relating y to t is: y = 810 * e^((1/11) * ln(972/810) * t)
(b) To find the number of fish after 21 years, we can plug t = 21 into the formula:
y = 810 * e^((1/11) * ln(972/810) * 21)
Calculating this value will give you the approximate number of fish after 21 years.
Learn more about Exponential growth