Doubt about the verb buy/bought

Hi, just need to know if both sentences are correct of first one is incorrect due to the use of buy instead bought:

Sentence 1:
When we went to the bookstore last night, we buy a book about engineering.

Sentence 2:
When we went to the bookstore last night, we bought a book about engineering.

Thanks in advance

Sentence 1 is incorrect.

The correct form is Sentence 2.

Bought is the past tense of to buy.

Quote:

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Originally Posted by vicente

Sentence 1 is incorrect.

The correct form is Sentence 2.

Bought is the past tense of to buy.

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Thank you so much for your reply

Indeed, when the main clause is in the past (went) or past perfect tense, the subordinate clause must be in the past (bought) or past perfect tense.

Quote:

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Originally Posted by nabylm

Indeed, when the main clause is in the past (went) or past perfect tense, the subordinate clause must be in the past (bought) or past perfect tense.

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LOL nabylm Now you're getting all academic on me. ;) You must have done well in your English classes. I only know how to speak it. Don't ask me to explain it. I barely got through my freshman English class. :rolleyes: