số abc = 100a + 10b + c = 5abc => a,b,c khác 0 => c = 5
100a + 10b + 5 = 25ab
20a + 2b + 1 = 5ab
vế trai là số lẻ => a,b phải lẻ (1,3,5,7,9)
Thử a= 9,7,5,3,1
chỉ có nghiệm a=1 b=7 c = 5
tim so tu nhien co 3 chu so ,biet rang so do gap 20 lan tong cac chu so cua no
1. tim so tu nhien co 3 chu so,biet so do gap 20 lan tong cac chu so cua no
2. tim so tu nhien co 2 chu so, biet rang neu lay so do chia cho hieu cua chu so hang chuc va hang don vi, thi ta duoc thuong la 28 du 1
3. tim 1 so tu nhien co ba chu so , biet rang neu chuyen chu so cuoi len truoc chu so dau ta duoc so moi hon so da cho 765 don vi
tim so tu nhien co 3 chu so , biet rang no tang gap n lan neu cong moi chu so cua no voi n (nla so tu nhien, co the gom mot hay nhieu chu so)
Tim so tu nhien co hai chu so biet rang so do gap doi tich cac chu so cua no
tim so tu nhien co hai chu so biet rang so do chia het cho tich cac chu so cua no
tim 1 so tu nhien co 3 chu so,biet so do gáp 20 lan tong cac chu so cua no
Tim so tu nhien co hai chu so khac nhau . Biet rang: hai chu so cua so do deu la so nguyen to . Tich cua so do voi cac chu so cua no la so co 3 chu so giong nhau duoc tao thanh tu chu so hang don vi cua so do.
1. Tim tat ca cac so co 2 chu so sao cho moi so gap 2 lan tich cua no?
2. Tim so nguyen to co 3 chu so biet rang neu viet so do theo thu tu nguoc lai thi ta duc 1 so la lap phuong cua 1 so tu nhien?
3. Tim so tu nhien co 4 chu so biey chu so hang nghin bang chu so hang don vi chu so hang tram bang chu so hang chuc va so do viet duoc duoi dang tich cua 3 so nguyen to lien tiep?
Tim 1 so tu nhien co 3 chu so , biet rang neu láy so do chia cho tong cac chu so cua no thi duoc thuong la 11
