Aide sur les probas

[Anonyme]

Voila 2 exzecice de maths , j ai fait le 1 et je trouve 7/12 comme resultat , par contre je comprend pas le 2 , pouvez vous me dire coment faire et me corriger le 1 merci d'avance

EXERCICE 1.
Every afternoon five o'clock Charles is having tea at his mother's.
In order to start the conversation he keeps saying either "I think it's raining" ou " I think it isn't raining ".
He is mistaken once out of three when it is raining, and once out of two when it is not raining nine time out of ten.
this afternoon , just after Big Ben rang five , he said : " I think it's raining".
Calculate the probability it is actually raining.


EXERCICE 2.
On the first day of beer week, Franz is of course wearing his leather trousers.They're held up by a belt and braces.Each brace has a one-in-five chance of breaking throughout the day , and the belt one chance in fifteen.

-Work out the probability that his trousers fall down that day.
-Considering that he didn't lose his trousers, work out the probabilitu taht his belt breaks.
(note : the belt's durability and that of the braces are independant factors.)

[tigri]

bonsoir
j'ai pas trouvé çà au 1)
on te demande la probabilité qu'il pleuve réellement, sachant qu'il a dit qu'il pensait qu'il pleuvait

[Anonyme]

tu reouve koi donc au 1?? et au 2