1 gio chi thu nhat lam duoc:1:12=1/12(ruong lua)
1 gio chi thu 2 lam duoc:1:16=1/16(ruong lua)
1 gio chi thu 3 lamduoc:1:18=1/18(ruong lua)
vay neu lam chung thi 1 gio ca 3 nguoi gat duoc so phan cua ruong lua la:1/12+ 1/16 +1/18=29/144(ruong lua) k va kb voi minh nhe!k neu thay minh lam dung!