Thread: Rule of 72

I have done part of this program so far. The Rule of 72 is used by bankers and politicians which states that if R% is the annual rate of inflation, then a fixed sum of money will decline in value by 50% in 72/R years
I need to prove that Rule of 72 is reasonable for inflation rates of from 1 to 25%

Code:

#include <iostream.h>
#include <iomanip.h>
#include <math.h>

int main()
{
	// Declare Variables
	double years;
	double rate;
	double calculate;
	int hold;
	
	//formula = abs(log10)(.5)/(log10(1+rate));
	
	// Prove Rule of 72 
	int r = rate;
	for (r = 1; r < 26; r++)
	{
		
		
		int y = years;
		for (y = 1; y < 73; y++)
		{
			years = years / 2;
		}
		
		calculate = abs(log10(.5))/(log10(1+rate));
	
		// Print Results to screen
		cout <<	"	Depreciation Chart in years to Test Rule 0f 72 " << endl;
		cout << "Rate of % Inflation " << setw(5) << "#years by Rule of 72 " << setw(5) << "Calculated # of years " << endl;
		cout << r << setw(5) << years << setw(5) << calculate << endl;
		break;
	}	

	cin >> hold;
	return 0;
}

This is my code so far. The formula is right because I looked it up in the internet. I have a problem printing to the output. I used a for loop and i want to start from 1 and increment it by 1 until it reaches 25 and i need it to print that and the years and calculated # of years.