Intermediate grammar exercise: third conditional

English grammar practice exercise, for intermediate learners.

In this exercise you will practise third conditional sentences.

Exercise instructions

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

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Structure of 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 told me if you'd (you had) known about it?
The third conditional – common mistakes
Common mistakes Correct version Why?
if I would have asked 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.
she would tell you If you had spoken to my mother, she would have told you where I was. The structure of the main clause is would + have + past participle.