Ta có:2,12,30,56,90....=1x2,3x4,5x6,7x8,.....Từ đó có Sh thứ 20 là 39x40=1560Đ/s:1560
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1) co bao nhieu so co 3 chu so ma ko chia het cho 5
2) tim so hang thu 100 cua day so: 1; 4;9;25;36...
3) tim phan so thu 100 cua day phan so:
1/2; 1/6; 1/12; 1/20; 1/30...
cho day so 2;12;30;56;90;...
tim so hang thu 20 cua day do
1.Cho day so sau: 4,7,10,13,....,100,103
a. tinh tong day so tren
b. so 50,76,106 co la so do cua day so do khong? neu thuoc day thi no la so hang thu bao nhieu cua day?
2. tim so co 2 chu so, biet rang lay so do chia tong cac chu so cua no thi duoc thuong la 5 du 12
Bai 1: Cho day so : 10; 13; 16; 19...
a) so 2002 la so hang thu bao nhieu cua day
b) Tim so hang Thu 107 cua day
Bai 2: tinh tong cua day so sau :
2; 4; 6; 8... 78; 80
Bai 3 : Cho day so
3; 6; 12; 24; 48...
Cac so 666; 2004 co thuoc day khong
Bai 4 : cho day 3; 18; 48; 93; 153...
a ) Tim so hang Thu 100 cua day
b ) so 11703 la so hang Thu bao nhieu cua day
Ai nhanh minh tick!
cho day so 3,8;48,93,153.................
tim quy luat cua day so viet tiep 2 so hang cua day
so 11703 la so hang thu bao nhieu
tim so hang thu 99 cua day so
11 ; 12 ; 13 ;16 ;17;18; 20; 21; 22
Cho day 3,18,48,93,153,.....
a) Tim so hang thu 100 cua day ?
b) So 11703 la so hang thu bao nhieu cua day ?
cho day so 102,108,114,120....tim so hang thu 45 cua day va tong cua day so vua tim dc
cho day so 2,3,5,8,12,17,23,...a)tim so hang thu 50 cua dayb)so 242 co thuoc day hay khong neu co thi la so hang thu bao nhieu cua day