a) 3 phân số đó là: 51/80    ,    52/80 và 53/80

bai 2 ket qua la 23

bài 1

a,

32 + 68 :17 x 5 - 29

= 32 + 20 -29

= 52 - 29

= 23

b,

15 x 48 - 30 x 24 - 125

= 720 - 720 -125

= 0-125

a,

32 + 68 :17 x 5 - 29

= 32 + 20 -29

= 52 - 29

= 23

b,

15 x 48 - 30 x 24 - 125

= 720 - 720 -125

= 0-125

b

Q=\(\frac{2}{6}+\frac{2}{12}+\frac{2}{20}+...+\frac{2}{9900}\)

Rồi giải tương tự như câu a là được

M=\(5\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{99}-\frac{1}{100}\right)=5\left(1-\frac{1}{100}\right)=5.\frac{99}{100}=\frac{99}{20}\)

\(\frac{85}{51}=\frac{85:17}{51:17}=\frac{5}{3}\)

Học tốt~

\(\frac{85}{51}=\frac{5}{3}\)

Tk nha mọi người

BAN QUY DONG:

\(\frac{1}{2}=\frac{6}{12};\frac{2}{3}=\frac{8}{12}\)

VẬY P/S Ở GIỮA \(\frac{6}{12}\)VÀ \(\frac{8}{12}\)LÀ \(\frac{7}{12}\)

TK MK NHA. ~'HỌC TỐT'~

Ta có : \(\frac{1}{2}=\frac{1\times3}{2\times3}=\frac{3}{6};\frac{3}{6}=\frac{3\times10}{6\times10}=\frac{30}{60}\)

           \(\frac{2}{3}=\frac{2\times2}{3\times2}=\frac{4}{6};\frac{4}{6}=\frac{4\times10}{6\times10}=\frac{40}{60}\)

Vì \(\frac{30}{60}< \frac{31}{60}< \frac{40}{60}\)nên phân số cần tìm là \(\frac{31}{60}\)

~ Hok tốt ~

~ Ủng hộ mik vs ạ ! Mơn nhiều ạ ~

a)\(\frac{16.17-5}{16.16+11}=\frac{16.17-16+11}{16.16+11}\)\(=\frac{16.\left(17-1\right)+11}{16.16+11}=\frac{16.16+11}{16.16+11}=1\)

b) \(\frac{45.16-17}{28+45.15}=\frac{45.\left(15+1\right)-17}{28+45.15}\)\(=\frac{45.15+45-17}{28+45.15}=\frac{45.15+28}{28+45.15}=1\)

c) \(\frac{7256.4375-725}{3650+4375.7255}=\frac{\left(7255+1\right).4375-725}{3650+4375.7255}\)\(=\frac{7255.4375+4375-725}{3650+4375.7255}\)\(=\frac{7255.4375+3650}{3650+4375.7255}=1\)

Câu C nhớ sửa 725 thành 7255 nha !

                                                       Bài giải

\(a,\text{ }\frac{16\cdot17-5}{16\cdot16+11}=\frac{16\cdot16+16-5}{16\cdot16+11}=\frac{16\cdot16+11}{16\cdot16+11}=1\)

\(b,\text{ }\frac{45\cdot16-17}{28+45\cdot15}=\frac{45\cdot15+45-17}{45\cdot15+28}=\frac{45\cdot15+28}{45\cdot15+28}=1\)

\(c,\text{ }\frac{7256\cdot4375-725}{3650+4375\cdot7255}=\frac{4375\cdot7255+4375-725}{4375\cdot7255+3650}=\frac{4375\cdot7255+3650}{4375\cdot7255+3650}=1\)

3/4, 11/12, 19/18, 7/6 

(học tốt)

3/4 ; 11/12; 19/18; 7/6 nha

a) Ta có : \(\frac{12}{48}< \frac{12}{47}\); \(\frac{12}{48}< \frac{13}{48}\)

=> \(\frac{12}{48}< \frac{13}{47}\)

b) Ta có : \(\frac{7}{13}=1-\frac{6}{13}\)

               \(\frac{17}{23}=1-\frac{6}{23}\)

Mà \(-\frac{6}{13}< -\frac{6}{23}\)=> \(\frac{7}{13}< \frac{17}{23}\)

Ta có: \(M=\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}+\frac{1}{55}\)

\(\Leftrightarrow\frac{1}{2}M=\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}+\frac{1}{110}\)

\(\Leftrightarrow\frac{1}{2}M=\frac{1}{6.7}+\frac{1}{7.8}+\frac{1}{8.9}+\frac{1}{9.10}+\frac{1}{10.11}\)

\(\Leftrightarrow\frac{1}{2}M=\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}+...+\frac{1}{10}-\frac{1}{11}=\frac{1}{6}-\frac{1}{11}=\frac{5}{66}\)

\(\Rightarrow M=\frac{5}{66}:\frac{1}{2}=\frac{5}{33}.\)

\(M=\frac{1}{21}+\frac{1}{28}+\frac{1}{36}+\frac{1}{45}+\frac{1}{55}\)

\(M=\frac{2}{42}+\frac{2}{56}+\frac{2}{72}+\frac{2}{90}+\frac{2}{110}\)

\(M=\frac{2}{6\cdot7}+\frac{2}{7\cdot8}+\frac{2}{8\cdot9}+\frac{2}{9\cdot10}+\frac{2}{10\cdot11}\)

\(M=2\left(\frac{1}{6\cdot7}+\frac{1}{7\cdot8}+\frac{1}{8\cdot9}+\frac{1}{9\cdot10}+\frac{1}{10\cdot11}\right)\)

\(M=2\left(\frac{1}{6}-\frac{1}{11}\right)\)

\(M=2\cdot\frac{5}{66}\)

\(M=\frac{5}{33}\)