Answer:
1/625
Step-by-step explanation:
In case of multiplication of numbers with same base, we add the powers.
This means that:
a^x * a^y = a^(x+y)
Applying this to the given, we will find that:
(5^-1) * (5^-3) = 5^(-1-3)
= 5^-4
= 1/625
Hope this helps :)