從?$1$?樓到?$12$?樓，中間經(jīng)過(guò)的樓層數(shù)為?$12 - 1=11($?層?$)；$?
?$ $?從?$9$?樓到?$12$?樓，中間經(jīng)過(guò)的樓層數(shù)為?$12 - 9 = 3($?層?$)；$?
?$ $?所以從?$9$?樓到?$12$?樓所用時(shí)間是總時(shí)間的?$3\div 11=\frac {3}{11}。$?
答：從?$9$?樓到?$12$?樓所用時(shí)間是總時(shí)間的?$\frac {3}{11}。$?
