全遇红灯的概率:1/2 *1/2 *1/3 *1/3 =1/36;
仅A不遇红灯:(1-1/2 )*1/2 *1/3 *1/3 =1/36;
仅B不遇红灯:1/2*(1-1/2 )*1/3 *1/3 =1/36;
仅C不遇红灯:1/2*1/2 *(1-1/3) *1/3 =2/36;
仅D不遇红灯:1/2*1/2 *1/3 *(1-1/3 )=2/36;
迟到概率:1/36+1/36+1/36+2/36+2/36=7/36
不迟到则为1-7/36=29/36
全遇红灯的概率:1/2 *1/2 *1/3 *1/3 =1/36;
仅A不遇红灯:(1-1/2 )*1/2 *1/3 *1/3 =1/36;
仅B不遇红灯:1/2*(1-1/2 )*1/3 *1/3 =1/36;
仅C不遇红灯:1/2*1/2 *(1-1/3) *1/3 =2/36;
仅D不遇红灯:1/2*1/2 *1/3 *(1-1/3 )=2/36;
迟到概率:1/36+1/36+1/36+2/36+2/36=7/36
不迟到则为1-7/36=29/36