Answer
The left side and the right side of the equation do not have the same dimensions so the equation is incorrect. It seems that the correct equation should be $d = \frac{1}{2}at^2$
Work Step by Step
$d = \frac{1}{2}at$
We can use dimensional analysis to check this equation.
The dimensions of the left side of the equation are [L].
The dimensions of the right side of the equation are $\frac{[L]}{[T^2]}\times [T] = \frac{[L]}{[T]}$
The left side and the right side of the equation do not have the same dimensions so the equation is incorrect. It seems that the correct equation should be $d = \frac{1}{2}at^2$
