Question

This may seem like a stupid question but I just started learning javascript about a week ago. I decided to try and automate my homework with javascript but I can’t figure out how to do this. It works as follows:

You are calculating how many decades it takes for a population to reach a certain number.

We’ll make this simple and make the growth rate .20. The population will start at 50 and we want it to reach 100.

So far this is what I have:

    function newPeople(start, growth) {
    var a = start * growth;
    var b = start + a;
    var c = Math.round(b);
    var d = c * growth;
    var e = c + d;
    var f = Math.round(e);
    return f;
    }

    newPeople(50, .20);

You can see that it can be done manually by creating a new set of variables each time, but how do I automate that?

Answer 1

This should work:

// start is the current population
// growth is the growth rate
// target is the target population
function newPeople(start, growth, target) {

    var pop = start;
    var years = 0;
    while(pop <= target) {
        years++; // increment year by one
        pop = pop + Math.floor(pop * growth);
    }

    // return what you need from the function here
    // "return years;" will give you the number of years it takes to go from "start" to "target"
    // "return pop;" will give you the actual population after "years" number of years
}