How to use "learnt" in a sentence

I learnt to use it quite well

For many years, Marius believed this, but when he was seventeen years old, he learnt the truth

But if she learnt the truth about Rebecca's death, she would become Maxim's enemy too

Going to the edge of the pit, I found a group of men in it - Henderson, Ogilvy, and a tall fair-haired man I afterwards learnt was Stent, the Astronomer Royal, with several workmen holding spades

At the time we could not understand these things, but later I learnt the meaning of these frightening black hills