In the past tense "can" becomes "could" or "was able to".

Example 1
"Can" becomes "was able to" when the action is a particular achievement in the past.
When we were young, I was able to beat you at tennis only once.

Example 2
"Can" becomes "could" when the action is a general ability that the person had.
When we were young, I could always beat you at tennis.

Example 3
"Can" also becomes "could" with certain 'verbs of perception': see, hear, taste, feel, remember, understand and guess. In other words, verbs which describe information taken in through the senses, or actions performed by the brain.
I could hear her scream.
She could remember a little Spanish from her schooldays.


Now read these sentences and change them into the past tense, using "could", or "was able to". Type the whole sentence in the empty text box, making any other changes which are necessary. Then click the answer box.


1. Of course I can find your house! I have a map.
2. They can play football very well.
3. She is very fast. She  can run 100 metres in eleven seconds.
4. I can climb hills, but not mountains.
5. I  can remember your face, but not your name.
6. I can get in to your house this morning because I have a key.
7.  I can understand his point of view.
8. As a  young person I can sleep deeply for hours.
9. Although it is dark in the room, I know he is there. I can sense his presence.
10. I can pass all my exams, despite my long illness.
11. It is very quiet. We can hear the wind.
12. I am a great swimmer. At the age of 15 I can swim across the English Channel in 18 hours.



In the future tense "can" becomes "will be able to", although "can" is used to when you are deciding now about something which will happen in the future.


1.When I have a car, I will be able to drive to school.
2.When I have more money, I will be able to pay you.

3.I can come on holiday with you in July.
4.I can be at your house by 8.30.

In Examples 3 and 4 a definite decision about the future is expressed.


Now read these sentences. Type the sentence again in the text box, but put it in the future tense. Use the correct future form of "can" together with the verb in brackets. Then click the answer box to see if you have used the right auxiliary correctly. 



1.  Work hard at school. Then you (find) a good job.
2. I've booked a hotel room for Saturday night, so we (stay) for the whole weekend.
3. I (attend) that business meeting this afternoon, because I've cancelled my dental appointment.
4. When I am 18, I (go) into pubs.
5. I've taken some holiday. Now we (fly) to Rio, like we planned.
6. I (drive) you to the station this afternoon, if you want.
7. If you practise regularly, you (play) the violin well.
8. OK. I (collect) your car from the garage on Friday.
9. We're fully booked this week. We (offer) you a room next week.  Will that be OK?
10. When you are retired, you (do) more in the garden.