Đáp án: cau a- co the viet duoc muoi hai so co hai chu so
Cau b- co the viet duoc ba muoi tam so co ba chu so
Cau c- co the viet duoc muoi hai so co ba chu so khac nhau
Giải thích các bước giải:a) vi ta co the ghep cac so 0,1,3,7 thanh cac so co hai chu so nhu sau : 10, 11, 13, 17, 30, 31, 33, 37, 70, 71, 73, 77
Cau d- co/the viet duoc muoi sau so co bon chu so khac nhau
Cau e- co the viet duoc hai muoi mot so co bon chu so khong lap lai qua hai lan
b) vi ta co the ghep cac so 0,1,3,7 thanh cac so co ba chu so nhu sau :
103,107,130,111,170,301,310,333,303,307,377,337,701,703,707,700,711,733,
777,710,730,731,713,770,771,773
c) vi ta co the ghep cac so 0,1,3,7 thanh cac so co ba chu so khac nhau nhu sau : 103,107,130,170,301,310,317,371,701,710,703,730
d) vi ta co the ghep cac so 0,1,3,7 thanh cac so co bon chu so khac nhau nhu sau:1037,1073,1307,1703,3017,3071,3170,3107,3701,3710,3170,7013,7031,7310,7130
e) vi ta co the ghep cac so 0,1,3,7 thanh cac so co bon chu so ko lap lai qua hai lan nhu sau : 1107,1103,1170,1130,3301,3307,3310,3370,7701,7703,7730,7710,1100,1133,1177,3300,3311,3377,7700,7711,7733