I am having trouble calculating speed...?

Question

OK. I am very frustrated because I have been working on this problem for 15 minutes and I just can't get to a solution. Here is the question: On a distant planet a freely-falling object has an acceleration of 20m/s/s. Calculate the speed an object dropped from rest on this distant planet acquires in 1.5 seconds. Note: Distance fallen from free fall, from rest= d=1/2gt^2. Please show me how you solved this problem!

Answer 1

v=u+at

u=0

a=20

t=1.5

wats so difficult....

Answer 2

Gravity acceleration is 20 m/s/s - so after one sec the speed is 20 m/s, then add another half sec and the speed would be 30 m/s after 1.5 sec.

Answer 3

20 m/s² * 1.5 sec = 30 m/s velocity