tim so tu nhien co hai chu so thoa man ba dieu kien sau.tong cac chu so cua no khong nho hon 7 tong binh phuong cac chu so khong lon hon 30.hai lan so duoc viet boi cac chu so cua so phai tim theo thu tu nguoc lai khong lon hon so do
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Tim so tu nhien co 2 chu so biet rang chu so hang chuc lon hon chu so hang don vi la 2 va so do lon hon tong cac binh phuong cac chu so cua no la 1.
bai1 tim so co hai chu so biet rang so moi viet theo thu tu nguoc lai la so co 2 chu so moi khi nhan voi so phai tim thiduoc tich la 3154so nho trong hai so do thi lon hon tong cac chu so cua no la 27bai2ban Hung dung so tu nhien de danh so trang 1-150 de danh so sach thi ban Hung can bao nhieu chu so bai3nguoi ta danh so nha tren mot danh pho tu 2-120.Hoi can dung bao nhien chu sobai411so co bon chu so voi cac chu so ngan ngin ngan tram ngan don vi lan luot la4chu so tu nhien lien tiep .Hoi so...
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bai1 tim so co hai chu so biet rang so moi viet theo thu tu nguoc lai la so co 2 chu so moi khi nhan voi so phai tim thiduoc tich la 3154so nho trong hai so do thi lon hon tong cac chu so cua no la 27
bai2ban Hung dung so tu nhien de danh so trang 1-150 de danh so sach thi ban Hung can bao nhieu chu so
bai3nguoi ta danh so nha tren mot danh pho tu 2-120.Hoi can dung bao nhien chu so
bai411so co bon chu so voi cac chu so ngan ngin ngan tram ngan don vi lan luot la4chu so tu nhien lien tiep .Hoi so nay tang bao nhieu nieu ta viet cac chu so cua no theo thu tu nguoc lai.
do ai giai duoc
Mot bqn khi tim tat ca cac so co 6 chu so biet tong cac chu so cua no la 48 va khi viet cac chu so do theo thu tu nguoc lai thi so do khong thay doi .hoi ban ay tim duoc nhieu nhat bao nhieu so thoa man yeu cau
ban an phai tim tat ca cac so co 3 chu so lon hon 500 ma tong cac chu so cua moi so do deu bang 12 dong thoi chu so hang don vi bang trung binh cong cua chu so hang tram va hyang chuc hoi ban an tim duoc nhieu nhat bao nhieu so thoa man yeu cau
Mot so co hai chu so bang 3 lan tong cac chu so cua no cong voi 7.Neu viet so do theo thu tu nguoc lai thi duoc so moi bang 7 lan tong cac chu so cua no cong voi 3.Tim so da cho
Ta gọi số đó là ab
Ta có :
ab = ( a + b ) x 3 + 7 ( 1 )
a x 10 + b = a x 3 + b x 3 + 7
a x 7 = b x 2 + 7
7 x a - 7 = b x 2
ba = ( b + a ) x 7 + 3 ( 2 )
b x 10 + a = b x 7 + a x 7 + 3
b x 3 = a x 6 + 3
b x 1 = a x 2 + 1
Từ 1 ta viết 2 thành :
b x 2 = a x 4 + 2
= > a x 4 + 2 = 7 x a - 7
= > 7 x a - 4 x a = 9
3 x a = 9
=> a = 3 , b = 7
Số đó là 37
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Ban An phai tim tat ca cac so co 3 chu so lon hon 500 ma tong cac chu so cua moi so do deu = 12, dong thoi chu so hang don vi = trung cong cua chu so hang tram va hang chuc. Hoi ban An tim duoc nhieu nhat may so thoa man yeu cau?
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tim tat ca cac so tu nhien có 2 chu so biet rang chu so hang don vi nho hon chu so hang chuc la 2 va tich cua chu so do cua no luon lon hon tong cua hai chu so cua nó la 34 don vi