A crew of four seemed like a reasonable working assumption.
On the surface that seems a reasonable assumption to make.
A more reasonable assumption might be 6 or 7 percent.
Considering the attention the three men receive, that is a reasonable assumption.
At least the only reasonable assumption is that she died.
In this case you are going to have to make some reasonable assumptions and then proceed as though they might be true.
For the most part this is a reasonable assumption to make.
It is a reasonable assumption that improvements can be made even to the best of schools.
If you accepted the theory, that was a reasonable assumption.
The error lay in a very simple but quite reasonable assumption which everyone made.