Solution:

For a body starting from rest with constant acceleration:

- Distance covered in the 5th second: \( s_5 = u + \frac{a}{2}(2n - 1) \), where \( u = 0 \) and \( n = 5 \):
\[
s_5 = \frac{a}{2} (9) = \frac{9a}{2}
\]

- Distance covered in 5 seconds: \( S = \frac{1}{2} a t^2 \), where \( t = 5 \):
\[
S = \frac{1}{2} a (5)^2 = \frac{25a}{2}
\]

Ratio of distances:
\[
\frac{s_5}{S} = \frac{\frac{9a}{2}}{\frac{25a}{2}} = \frac{9}{25}
\]

Thus, the ratio is 9:25.