The second example is not preferred. The rule is somewhat vague, something along the lines of "if the thing being measured is considered a unit, use singular."

4 tsps. of sugar was called for by the recipe

Otherwise if your thinking of the parts individually, use plural:

2 cups of flour were needed, one for the cake and one for the bread.

nibake wrote:The second example is not preferred. The rule is somewhat vague, something along the lines of "if the thing being measured is considered a unit, use singular."

4 tsps. of sugar was called for by the recipe

Otherwise if your thinking of the parts individually, use plural:

2 cups of flour were needed, one for the cake and one for the bread.

4 tsps. of sugar
2 cups of flour
i think gramatically it looks same here
well i guess we cannot use were and was just saying 'ok i consider this as unit and this as not'
bit confused

It is a bit confusing, and yes, gramatically there is no difference. As a matter of fact, you could interchange things like "2 cups of flour" between the sentence. Ultimately you have to look at the context of the whole sentence.

Here are a couple more confusing examples:

The family is an important part of society.
The family are arriving for the wedding at different times.

The jury is going to decide today.
The jury are returning to their homes tomorrow.

Singular verbs when we are contextually using the subject as singular. Plural if we are talking about things as individual parts. If you say "but wait, isn't that subjective?" I agree with you. If you like everything to be clean cut you should probably go over to the math forums.

i think 'family are' is totally incorrect so is 'jury are'
can you show me an instance where it is used?

thanks

I know it seems odd. The example is from a subject/verb agreement section from a Kaplan SAT prep book.