All is a determiner. It is used before a plural noun. We use all before a noun without a determiner. All and all of are both possible before a noun with a determiner.

Study the examples given below.

• All my students work hard. / All of my students work hard.
• All the lights were out. / All of the lights were out.
• All those mangoes are ripe. / All of those mangoes are ripe.
• All the invitees have turned up. / All of the invitees have turned up.
• All children need love. (NOT All of children need love.) (We cannot use of here because the noun children does not have another determiner (article, possessive or demonstrative) with it.)

Before a pronoun we use all of.

• All of us want to go. (NOT All us want to go.)
• All of them have arrived. (NOT All them have arrived.)

Fill in the blanks with all or all of.

1. …………………. his books are best sellers. (All / all of)

2. ……………………. my friends are non-smokers. (All / all of)

3. ………………… us can swim. (All / all of)

4. …………………. the students have submitted their work. (All / all of)

5. You have eaten ………………….. the cake. (all / all of)

6. …………………. the books are on the table. (All / all of)

7. …………………… my children love riding. (All / all of)

8. Have you invited ………………….. them? (all / all of)

9. …………………. flowers are beautiful. (All / all of)

10. Not …………………. birds can fly. (all / all of)

Answers

1. All / all of his books are best sellers.

2. All / all of my friends are non-smokers.

3. All of us can swim.

4. All / all of the students have submitted their work.

5. You have eaten all /all of the cake.

6. All / all of the books are on the table.

7. All / all of my children love riding.

8. Have you invited all of them?

9. All flowers are beautiful.

10. Not all birds can fly.