public class Interest {
	public static void main(String[] args) {

		// How many years does it take for the principal to double?

		final double rate = .06; // 6 percent
		final double factor = 1 + rate;
		final double start = 100;
		double amount = start;
		int year = 0;

		do {
			amount = amount * factor; // amount *= factor;
			year = year + 1; // ++year
			System.out.println(year + "\t" + amount); // tab character
		} while (amount < 2 * start);

		System.out.println();
		System.out.println(Math.log(2.0) / Math.log(factor));
	}
}