Calculate and give the answer as a fraction.

a) [[$ \sqrt {\displaystyle\frac {9} {25}} = $]]


b) [[$ \sqrt {\displaystyle\frac {4} {81}} = $]]


c) [[$ \sqrt {\displaystyle\frac {1} {16}} = $]]


d) [[$ \sqrt {\displaystyle\frac {1} {36}} = $]]


e) [[$ \sqrt {\displaystyle\frac {49} {100}} = $]]


f) [[$ \sqrt {2\displaystyle\frac {1} {4}} = $]]