\(\bf {{ a}}\%\ of\ b \implies \cfrac{{{ a}}}{100}\cdot b\implies {{ a}}\div 100\cdot b\\\\
-----------------------------\\\\
thus
\\\\
\begin{cases}
{{ 1}}\%\ of\ 400 \implies \cfrac{{{ 1}}}{100}\cdot 400\implies {{1}}\div 100\cdot 400\\
--------------\\
{{ \frac{1}{2}}}\%\ of\ 400 \implies \cfrac{{{ \frac{1}{2}}}}{100}\cdot 400\implies {{\frac{1}{2}}}\div 100\cdot 400
\end{cases}\)
you tell us