Your grades depend on the amount of work you put into your studies.

The word number is used with countable words.

Frank and I surprised at number of birds in the zoo.

• ANOTHER x OTHER

   The word another is always singular. It is written as one word. It refers to an indefinite, different member of a series. It is not used to refer to the second of a known pair. Another occurs eitheir alone or before a singular noun or the word one.

If you do not like that pie, put on another. You have a lot.
This short is soiled. I´m going to put pn another one.
It is very cold. You had better put on another sweater.
Wouldn´t you like to have another piece of pie?

There are a number of expressions with the words one... another.

My friend Jerry is always busy with one thing or another.
A hobo is a person who wanders from one place to another.

The word other may be used before either a singular or a plural noun. If no noun follows, other, is used to reffer to a singular noun, and others is used to refer to a plural noun. The other is used for the second of a known pair, and the others is used for all the remainings members of a known group.

The secretary told the applicant to come back some other time.
Elizabeth was glad to go with the other girls.
That movie was more interesting than any other I have seen recently.
It is true that some books are duller than others.
The little girl slowly closed one eye and then the other.
Mr. Brown carried the heavy bag, and the children took all the others.