Intermediate grammar exercise: third conditional

English grammar practice exercise, for intermediate learners.

In this exercise you will practise third conditional sentences.

Instructions: Put the words in brackets into the correct form to make third conditional sentences:

questions go herescore goes here

Structure of the third conditional
positive negative question
If I'd (I had) known you were coming, I would have waited for you. If she hadn't (had not) been ill, she would have gone to the cinema. Would you have done it if you'd (you had) known earlier?

The third conditional - common mistakes
Common mistakes Correct version Why?
If I would have asked him, he would have helped me. If I had asked him, he would have helped me. In the if-clause we use the past perfect (had + past participle). We don't use 'would' or 'would have' in the if-clause.
If you had spoken to my mother, she would tell you where I was. If you had spoken to my mother, she would have told you where I was. The main clause has
would + have + past participle.