GMAT数学
whichofthefollowingliststhenumberofpointsatwhichacirclecanintersectatriangle?
a)2and6only
b)2,4and6only
c)1236
d)12346
e)123456
完全不知道这个是干什么的,
Tanyaprepared4differentletterstobesentto4
differentaddresses.Foreachletter,
shepreparedanenvelopewithitscorrectaddress.Ifthe4lettersaretobeputintothe4
envelopesatrandom,whatistheprobabilitythatonly1letterwillbeput
intotheenvelopewithitscorrectaddress?
是不是有什么公式要记?