How Long Something Stays in Air Calculation. Help Needed

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A kangaroo jumping to a height of 3.0 meters will remain in the air for a total time calculated using the equation d = vf(t) - 1/2 a(t)². The initial attempt yielded a time of 0.78 seconds, which only accounts for the ascent to the peak height. Since the total time in the air includes both ascent and descent, the correct duration is double that, resulting in approximately 1.56 seconds. The confusion arose from not initially considering the descent time, which is equal to the ascent time. Therefore, the total time in the air for the kangaroo's jump is 1.56 seconds.
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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=vf(t) - 1/2 a (t)2

I Think?


The Attempt at a Solution


Defined all variable
d=3.0 m
a=9.81 m/ss
vf=0m/s2

then:
d=vf(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.
 
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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?
 
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