Looking at following stock. In the details where it says Div/yeild 0.20/3.90 As far as I understand 0.20 cents is amount paid per share. How does the yield of 3.90 gets calculated?

Looking at following stock. In the details where it says Div/yeild 0.20/3.90 As far as I understand 0.20 cents is amount paid per share. How does the yield of 3.90 gets calculated?

The dividend is for a quarter of the year, three months. 80 cents is 3.9% of $20.51. Presumably the Div/yield changes as the stock price changes. On Yahoo, they specify that the yield is based on a particular stated date. So it's only the exact number if the stock trades at the price on that date.
However, you have to remember that not all dividends are paid quarterly. For example one stock I recently purchased has a price of $8.03 and the Div/yield = 0.08/11.9 .
$.08 * 4 = $0.32 which is only 3.9% (But this stock pays monthly dividends).
$.08 * 12 = $0.96 which is 11.9 %.
So over the course of a year assuming the stock price and the dividends didn't change you would make 11.9%