Hai thế kỷ rưỡi =.........năm. Số thích hợp để điền vào chỗ chấm là: 

A. 250                  B.205                   C.25                     D. 2500

chọn A

HT và $$$

a) <

b) =

c) >

d) <

e) <

\(\frac{2010}{2011}< \frac{2011}{2012}\)

\(\frac{11}{12}=\frac{22}{24}\)

\(\frac{25}{30}>\frac{25}{49}\)

\(\frac{1}{5}< \frac{3}{8}\)

\(\frac{1995}{1997}< \frac{1995}{1996}\)

a )

2 / 3 + 5 / 4 = 8 / 12 + 15 / 12 = 23 / 12

b )

15 / 25 + 6 / 21 = 3 / 5 + 2 / 7 

                       = 21 / 35 + 10 / 35

                       = 31 / 35

c ) 

4 / 3 - 11 / 15 = 20 / 15 - 11 / 15

                    = 9 / 15

d )

12 / 10 - 2 / 5 = 12 / 10 - 4 / 10

                    = 8 / 10

                    = 4 / 5

a=23/12

b=31/35

c=3/5

d=4/5

a) \(\frac{2}{5}+\frac{9}{15}=\frac{2}{5}+\frac{3}{5}=\frac{5}{5}=1\)

b) \(\frac{15}{45}+\frac{25}{30}=\frac{1}{3}+\frac{5}{6}=\frac{2}{6}+\frac{5}{6}=\frac{7}{6}\)

c) \(\frac{28}{32}+\frac{45}{72}=\frac{7}{8}+\frac{5}{8}=\frac{12}{8}=\frac{3}{2}\)

d) \(\frac{8}{28}+\frac{5}{30}=\frac{2}{7}+\frac{1}{6}=\frac{12}{42}+\frac{7}{42}=\frac{19}{42}\)

a) \(\frac{2}{5}+\frac{9}{15}\)=\(\frac{2}{5}+\frac{3}{5}=\frac{2+3}{5}=1\)

b)\(\frac{15}{45}+\frac{25}{30}=\frac{1}{3}+\frac{5}{6}=\frac{2}{6}+\frac{5}{6}=\frac{2+5}{6}=\frac{7}{6}\)

c)\(\frac{28}{32}+\frac{45}{72}=\frac{7}{8}+\frac{5}{8}=\frac{7+5}{8}=\frac{12}{8}=\frac{3}{2}\)

d)\(\frac{8}{28}+\frac{5}{30}=\frac{2}{7}+\frac{1}{6}=\frac{12}{42}+\frac{7}{42}=\frac{12+7}{42}=\frac{19}{42}\)

đáp án là B

ý B nhé bạmn

a) 40 x X = 1400

           X = 1400:40

           X = 35

b) x : 13 = 205

          x = 205 x 13

          x = 2665

a, 40 x \(x\) = 1400

       \(x\) = 1400 : 40

       \(x\) = 35

b, \(x\) : 13 = 205

           \(x\) = 205 x 13

           \(x\) = 2665

d kkkk

d

bai toan nay 

(a+b) x 2=88 => a+b=44

(b+c) x 2= 148 => b+c=74

(a+c) x 2=108 => a+c=54

(c+d) x 2=208 => c+d=104

(b+d) x 2=188 => b+d=94

(a+d) x 2=148 => a+d= 74

=> a+b+b+c+a+c+c+d+b+d+a+d = 44+74+54+104+94+74

=> 3 x a + 3 x b + 3 x c + 3 x d = 444

3 x (a+b+c+d) = 444

a+b+c+d = 444 : 3

a+b+c+d = 148

a, 3 cm = \(\frac{3}{10}\)dm. Đ

c, 1367 mm = \(\frac{1367}{100}\)m. S

b, \(\frac{312}{1000}\)m = 312 cm. S

d, 25 dm = \(\frac{25}{10}\)m. Đ