I was going through an article where it's written:
"For example, if you hold two hearts, and there are two on the flop, you have nine outs to hit your draw, giving approximation of 18 percent to hit on the turn, or an 36 percent to hit by the river. This shortcut can be used in conjunction with pot odds to assess if your draw is worth continuing with."
I didn't understand how this 18 and 36 percent are calculated. If I have 4 hearts out of 47 cards and 9 outs left to hit at the turn, 9/47 = 19% approximately. If I don't hit on the turn, then at the river it should be 9/46 = 13% approximately. Then how is it 18% and 36%? Am I calculating it wrong?