“One hundred pounds” is considered singular when referring to a specific quantity of weight, because it’s a singular amount, even though “pounds” is plural in form.
For example:
- “One hundred pounds is a lot of weight to lift.”
However, if you’re talking about more than one quantity of a hundred pounds, then it would be plural:
- “Three hundred pounds are needed for the project.”
In short, it’s treated as singular when you’re talking about one hundred of anything (like weight, money, etc.).