number of fish

Question

The number of a particular fish in thousands x years after 1975 can be modeled by f(x)equals=221(0.87)x.

Estimate the year when the number of these fish reached 98 thousand.

 

The number of these fish reached 98 thousand in the year?

Answer 1

I must assume that the x on the right side expression for f(x) is intended to be an exponent, because otherwise the two decimal values found there would have been resolved into a single constant factor.

Here's what to do.  First, set 221(0.87)^x = 98.

Second, divide both sides by 221; now you have an exponential equation and to get at x you must take logarithms.

This gives you ln (98/221) = xln0.87 so x = 5.8393 or about 6 years after 1975.

 

Answer: 1981