1.cac so le lien tiep tu 211den 971 co bao nhieu chu so?

2.tong cua 100 so chan dau tien la bao nhieu?

3.tim a va b biet a+b=11 va b,a -a,b=2.7

co 45 lit dau .hoi co them bao nhieu lit dau nua de so dau cu gap doi so dau da cong .so dau moi la so co 2 chu so  tong 2 chu so do la 10

cho a la 1 so chinh phuong co 4 chu so biet 2 chu so dau va 2 chu so cuoi cua giong nhau hoi a la bao nhieu

100 - 99 cong 98 - 97 cong 96 - 95 cong  BA CHAM cong 4 - 3 cong 2

100 - 5 -5 - BA CHAM -5 [co 20 so 5]

99 - 9 -9 - BA CHA [co 11 chu so 9

help me please

2¹⁰⁰ co bao nhieu chu so? chu so dau tien ben trai la chu so may?

- 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 3 thung dau ,thung thu nhat co 256l.Biet 1/4 so dau thung thu nhat it hon 1/3 so dauthung thu hai la 14l nhung nhieu hon 1/5 so dau thung thu ba la 22l.Hoi ca 3 thung co bao nhieu lit dau?

1)co bao nhieu so tu nhien co ba chu so la ba so tu nhien lien tiep tu nho den lon neu viet so ay theo thu tu nguoc lai cua cac chu so ay theo thu tu nguoc lai cua cac chu so thi so moi hon so cu la bao nhieu?

tinh nhanh:

a)100-94+90-84+80-74+70-64+60-54

b)5.125.20.16

c)36.(140+97)+73.(232+68)

d)5+9+13+...+2005+2009+2013

e)3+6+9+...+108

f)1+2+4+8+...+4098

Trong mot dot thi dua lop 2b co so ban dat diem 10 la 1 so tu nhien lon nhat co 2 chu so ma tong 2 chu so do la 3 .So ban dat diem 9 nhieu hon  so ban dat diem 10 la 12 ban .Hoi lop 2b co bao nhieu ban dat diem 9.