Gọi số cần tìm là ab.
Theo đề bài ta có:
ab=21.(a-b)
10a+b=21a-21b
11a=22b
a=2b
Với b=1 thì a=2.
.....
Với b=4 thì a=8.
Vậy có 4 số.
Chúc em học tốt6^
co bao nhieu so co ba chu so ma trong cac so do tong hai chu so o hang tram va hang chuc bang chu so hang don vi
Tim so le co bon chu so,biet chu so hang chuc gap 3 lan chu so hang don vi,chu so hang tram gap 2 lan chu so hang chuc va chu so hang nghin gap 4 lan chu so hang don vi
Tim so le co bon chu so,biet chu so hang chuc gap 3 lan chu so hang don vi,chu so hang tram gap 2 lan chu so hang chuc va chu so hang nghin gap 4 lan chu so hang don vi.
Tim mot so chan co nam chu so khac nhau biet rang chu so hang chuc nghin gap ba lan chu so hang don vi chu so hang nghin gap 5 lan chu so hang chuc va chu so hang tram gap 4 lan chu so hang chuc .
tim so co hai chu so biet chu so hang chuc gap ba lan chu so hang don vi va neu doi cho hai chu so do cho nhau thi duoc so moi nho hon so dau 18 don vi
tim so tu nhien co hai chu so biet rang neu viet chu so 0 xen giua so hang chuc va hang don vi cua so do ta duoc so moi gap 10 lan so phai tim neu viet chu so 1 vao ben traiso vua nhan thi so do gap len 3 lan
mot so co hai chu so biet tong cac chu so cua no la 8 hieu cac chu so cua cua no la 4 va chu so hang chuc lon hon hang don vi so do la so nao
tim so co 3 chu so lon nhat co cac chu so khac nhau ma cac chu so hang don vi bang trung binh cong cua chu so hang tram va chu so hang chuc . tim so do
tim mot so co hai chu so biet neu xen chu so0 vao giua hang chuc va hang don vi thi so do gap len 10 lan neu viet chu so 1 vao ben phai so do thi so moi gap so cu 3 lan
