To answer this we need to use the acceleration of gravity which is 9.81 m/s^2. This means that an object of any size accelerates at 9.81 m per second every second. It's the rate of change of speed. After 1 second it is moving at a speed of 9.81 m/s; after 2 seconds its speed rises to 2*9.81=19.62 m/s. The average speed over the 2 seconds is 19.62/2=9.81 m/s. In that time the distance fallen is 2*9.81=19.62 m. Therefore the height of the ball is 70-19.62=50.38 m. This is 50.4 m to the nearest tenth.
If it takes t seconds to hit the ground its speed will be 9.81t m/s when it hits the ground. Its average speed is 9.81t/2=4.905t. Distance=average speed*time=4.905t^2=70. Therefore t=sqrt(70/4.905)=3.78 seconds, or 3.8 sec to the nearest tenth.