Concept:
For the same amount of work,
\[
\text{Men} \times \text{Days}
=
\text{Constant}
\]
This is the principle of inverse proportion.
Step 1: Assume the original number of persons is \(x\).
Initially,
\[
x \text{ persons}
\]
complete the work in
\[
60 \text{ days}
\]
Hence total work:
\[
60x
\]
man-days.
Step 2: Form the second condition.
After hiring 8 additional persons,
\[
x+8
\]
persons complete the work in
\[
60-10=50
\]
days.
Thus,
\[
50(x+8)
\]
man-days.
Since total work remains unchanged,
\[
60x=50(x+8)
\]
Step 3: Solve the equation.
\[
60x=50x+400
\]
\[
10x=400
\]
\[
x=40
\]
Therefore, the number of persons originally hired was
\[
\boxed{40}
\]