The past progressive is used to describe an activity that was in progress at a point in time in the past (e.g., at 5:20) or at the time of another action (e.g., when Mary called).

  • I was in the library at 7 P.M. yesterday. Mary came to the library at 7:10 P.M. I was studying when Mary¬†came to the library.
  • I went to bed at 11:00. The phone rang at 12:00. I was sleeping when the phone rang.

when = at that time
while = during that time

when and while have the same meaning.

  • I was studying when the phone rang.
  • The phone rang while I was studying.

When two actions are in progress at the same time, the past progressive can be used in both parts of the sentence.

  • While I was studying, my sister was watching TV.

Statement

{ I – She – He – It } was studying when you called.
{ You – We – They } were studying when I called.

Negative

{ I – She – He – It } was not (wasn’t) studying when you called.
{ You – We – They } were (weren’t) studying when I called.

Question

Was { I – she – he -it } studying when Mary called?
Were { you – we – they } studying when I called?

Short Answer

Yes { I – she – he – it } was. / No, { I – she – he – it } wasn’t.

Yes, { you – we – they } were. / No, { you – we – they } weren’t.