How Long Something Stays in Air Calculation. Help Needed

[student54321]

Homework Statement

Jumping straight up, how long will a kangaroo remain in the air if it jumps through a height of 3.0m?

Homework Equations

d=v_f(t) - 1/2 a (t)²

I Think?

The Attempt at a Solution

Defined all variable
d=3.0 m
a=9.81 m/s^s
v_f=0m/s²

then:
d=v_f(t) - 1/2 a (t)²
3.0=0 - 4.905(t)²
0.61=(t)²
t=Square root of 0.611
t=0.78

I got the wrong answer. But when I multiplied my answer by two I got the right answer. Don't know why so I'll need some help here.

And I know I skipped some calulation steps in my answer, I have them written on paper.

 

[student54321]

Just thought about it. Is it because what goes up must come down? So it needs to be 2 times the time, I just calculated for the time to the top of the parabola. Am I right?