Bài giải:
gọi số cần tìm là ab(a khác 0;a,b<10).Theo bài ra ta có:
ba=ab.4+3
=>10b+a=40a+4b+3
=>10b-4b=40a-a+3
=>6b=39a+3
=>2b=13a+1
2b<19 =>13a+1<19
=>13a<18
=>a<2 =>a=1 =>b=(13.1+1):2=7
vậy số cần tìm là 17
khi doi cho chu so hang chuc va chu so hang don vi cua 1 so cho nhau thi ta duoc 1 so moi nho hon so ban dau 26 don vi.tim so ban dau biet rang trung binh cong cac chu so cua no bang 7 va so do co 3 chu so
tim mot so co hai chu so biet rang so do gap 7 lan tong cua no va chu so hang chuc hon chu so hang don vi la 4
tim mot so co 3 chu so,biet rang chuyen chu so cuoi len dau ta duoc1 so lon hon 5 lan so da cho la 25 don vi
tim mot so co 3 chu so,biet rang chuyen chu so cuoi len dau ta duoc1 so lon hon 5 lan so da cho la 25 don vi
tim so co 2 chu so biet rang so do hon 3 lan chu so hang don vi cua no la 4
tim so co 4 chu so biet rang chu so tan cung cua so do la so 8 va neu chuyen chu so 8 nay len dau thi ta duoc mot so hon so do la 6192 don vi
tim so co hai chu so biet rang tong hai so cua so do la 15 va biet eu doi vi chi hai so cua so do cho nhau thi ta duoc so oi hon so phai ti 27 don vi
tong cua 3 so la 1019,535 tim ba so do biet rang doi dau phay cua so thu nhat sang ben phai 1 chu so ta duoc so thu hai . doi dau phay cua so thu nhat sang ben trai mot chu so ta duoc so thu ba
tim so co hai chu so biet rang neu doi cho hai chu so cua so do cho nhau ta duoc so moi hon so cu 45 don vi
