What is the best way to find the truth?

i want to know the age of aisah when she married mohammad. i have seen ages varing from 13 to 42. so where can i find the exact age of aisha in the hadiths. the hadiths were written by devout followers of mohammad and i have yet to find a reason why they would lie about their beloved prophet. the hadiths have existed for over 1,400 years and if they were wrong they would surely have been removed by now? so where can i find the exact age of aisha in the hadiths when she married the prophet, mohammad?