Basic physics energy problem?

I did a lab in physics where a ball was rolled down a ruler which was at a slant and then across the table onto the floor. We had to predict where the ball would land. I was correct and it landed 23 cm away from the table edge......however when i went back and looked at my work i did it wrong.......so here are the figures and why did i get the right answer?

the ruler was slanted by placing books on one side. The book was 3 cm.

The ball rolled across the table 1 m from the end of the ruler.

It took the ball 1.69 seconds to cross the 1m table.

The table was 88.7 cm away from the floor.

The ball went about 23 cm........and i did

9.8 (.03)=v^2

.5322 m/s

which is right......however....it should be 9.8 (.03)=1/2 v^2

which gives a different answer

please help