Logic-cake

My teacher hasn't explained much, and I'm not sure how to get the answer to these problems. If a projectile is fired straight up at a speed of 30 m/s, the total time to return to its starting point is about___. Supposedly the answer is 6 seconds, but I don't see how. Wouldn't I divide 30 m/s by the acceleration of gravity to get about 3 seconds? Also, I don't understand the answer to this one: The vertical height attained by a basketball player who achieves a hang time of a full one second is about___. and the answer is supposedly 1.2 meters. I tried to substitute the values into the equation [math] d= \frac {1}{2}gt^{2}[/math], where g is approx. [math]10 m/s^{2}[/math] and [math]t[/math], the hang time, is 1 second, and got the value 5. Am I doing something wrong, or is this right? And one more. If a projectile is fired beneath the water, straight up, and breaks through the surace at a speed of 13 m/s, to what height above the water will it ascend? Do I even have enough information to solve this one? Would I not need to know how deep the object is under water before it's fired? Thanks in advance for your help.