1 .trung binh cong cua hai phan so la 5/12 .neu tang phan so thu nhat gap 2 lan thi trung binh cong cua chung bang 2/3 .tim hai phan so do .
2.trung binh cong cua ba phan so la 13 /36 .neu tang phan so thu nhat gap 2 lan thi trung binh cong cua chung bang 19/36 ,cho biet phan so thu hai lon hon phan so thu ba 1 /12. tim ba phan so do .
trung binh cong cua 3 phan so la 31/90 . neu tang so thu 2 lan thi trung binh cong 3 so la 23/45 . biet so thu 2 hon so thu 3 la 2/15 tim so thu nhat
tbc cua 3 so la 98,9 . tim st1 biet rang st1 bang trung binh cong 2 so con lai
trung binh cong cua 2 so la 117 tim 2 so do biet rang neu viet them chu so 1 vao ben trai so be thi duoc so lon tim
tim 2 so biet hieu cua 2 so do la 68 va biet neu dem st1 chia cho 1/4, st2 chia cho 1/5 thi duoc ket qua giong nhau
trung binh cong cua 3 so la3/5.ST3bang trung binh cong cuaST1 vaST2. ST1 hon ST2 la 1/4.\
tim 3 so do
trung binh cong cua 3 so la 148 . biet rang neu viet them so chu so 0 vao ben phai so thu nhat thi duoc so thu 2 .viet them so 3 vao ben phai so thu nhat thi duoc so thu 3.tim trung binh cong so thu 1 va so 3
tim 2 so biet hieu la 95 va neu dem st1 chia cho 4, st2 chia cho 5 thi duoc ket qua bang nhau.
Tim ST1 .Biet rang viet them chu so 3 vao ben trai ST1 ta duoc ST2.Biet ST2 gap 7 lan ST1 ,ST1 co 2 chu so