how old was aragorn?
 

in the tales of aragorn and arwen at the end of lotr is says he's nine and forty years, so is he 940?

No...nine and forty means 49.

He Coulden't have been 940 because ELros was only given a lifespan of 500 years and I think he was the oldest man.

Aragorn was born March 1, 2931 TA, so when Elrond sailed west on September 29, 3021, he was 90 years old. He died in 120 FA, meaning he was about 210 at death.