If you're picturing a stress-free retirement where you live off investment interest, use this easy formula to calculate how much of a principal you'll need.

To find an investment's interest rate, substitute price, face value, and duration into a formula. For T-bills, subtract purchase price from face value, divide by face value, adjust for term. Online ...

India celebrates National Mathematics Day on December 22 to commemorate the birth anniversary of the Indian mathematician Srinivasa Ramanujan. He shaped twentieth-century mathematics with his ...