Cho số tự nhiên đó có dạng ab(có gạch trên đầu)
Khi a=1 thì ta có số:10
____=2___________:20;21
____=3___________:30;31;32
____=4___________:40;41;42;43
____=5___________:50;51;52;53;54
...
Khi a=9 thì ta có số:90;91;92;93;94;95;96;97;98
Vậy số các số mà hàng chục lớn hơn hàng đơn vị là:1+2+3+4+5+6+7+8+9=45(số)
co bao nhieu chu so tu nhien co hai chu so ma chu so hang chuc lon hon chu so hang don vi
CO BAO NHIEU SO TU NHIEN CO 2 CHU SO MA CHU SO HANG CHUC NHO HON CHU SO HANG DON VI
Co bao nhieu so tu nhien co hai chu so sao cho moi so chu so hang chuc lon hon chu so hang don vi ?
co bao nhieu so co 2 chu so ma chu so hang chuc lon hon chu so hang don vi
co bao nhieu so tu nhien co 2 chu so trong do chu so hang chuc nho hon chu so hang don vi la 5 ?
- tim so chu so chan co 4 chu so
- viet tat ca cac so tu 100 den 999phai dung bao nhieu chuvso 9
-co bao nhieu so le co 3 chu so
- viet 1000 sdo tu nyhien dau tien hoi chu so 3 cco mat bao nhieu lan
-viet tap hop cac so tu nhien co 2 chu so trong do a ) chu so hang chuc nho hon hang don vi la 4 b) chu so hang chuc gap 3 lan chu so hang don vi c) chu so hang chuc nho hon chu so hang don vi ( tong 2 chu so = 12)
co bao nhieu so tu nhien co hai chu so trong do chu so hang chuc nho hon chu so hang don vi la 5
viet bang cah liet ke cac phan tu cua cac tap hop sau:
a) tap hop A cac so tu nhien co 2chu so ma chu so hang chuc lon hon chu so 3
b) tap hop B cac so tu nhien co 2 chu so ma chu so hang don vi gap doi hang chuc
c) tap hop C cac so tu nhien co 2 chu so ma trong so do co it nhat 1 chu so 4
Q la tap hop so tu nhien co 2 chu so ma trong moi so chu so hang chuc lon hon chu so hang don vi la 2 . tinh so phan tu cua tap hop Q
