Given,
A ball is thrown vertically upward from the ground at the speed of 34m/s.
At t he heighest position the velocity is zero.
Thus the time taken to reach the top is
So to reach the group from the top it woukd require the same time.'
Thus total time required to reach the ground is
3.46s+3.46s=6.92s
The total time is 6.92 sec.