  DNA Self-Assembly has emerged as an interdisciplinary field with many
intriguing applications such DNA bio-sensor, DNA circuits, DNA storage, drug
delivery etc. Tile assembly model of DNA has been studied for various
computational primitives such as addition, subtraction, multiplication, and
division. Xuncai et. al. gave computational DNA tiles to perform division of a
number but the output had integer quotient. In this work, we simply modify
their method of division to improve its compatibility with further computation
and this modification has found its application in computing rational numbers,
both recurring and terminating, with computational tile complexity of
$\mathcal{O} (1)$ and $\mathcal{O} (h)$ respectively. Additionally, we also
propose a method to compute square-root of a number with computational tile
complexity of $\mathcal{O} (n)$ for an n bit number. Finally, after combining
tiles of division and square-root, we propose a simple way to compute the
ubiquitously used irrational number, $\pi$, using its infinite series.
