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Bài 2:

6000:30=600:3=200

5462:2=2731

45678:6=7613

Bài 1:

\(36\cdot50=36\cdot5\cdot10=180\cdot10=1800\)

\(59\cdot60=59\cdot6\cdot10=354\cdot10=3540\)

\(90\cdot40=90\cdot4\cdot10=360\cdot10=3600\)

a: \(\dfrac{11}{42}=\dfrac{11\cdot1}{42\cdot1}=\dfrac{11}{42}\)

\(\dfrac{5}{6}=\dfrac{5\cdot7}{6\cdot7}=\dfrac{35}{42}\)

 b: \(\dfrac{40}{7}=\dfrac{40\cdot4}{7\cdot4}=\dfrac{160}{28}\)

\(\dfrac{10}{28}=\dfrac{10\cdot1}{28\cdot1}=\dfrac{10}{28}\)

c: \(\dfrac{4}{15}=\dfrac{4\cdot4}{15\cdot4}=\dfrac{16}{60}\)

\(\dfrac{14}{60}=\dfrac{14\cdot1}{60\cdot1}=\dfrac{14}{60}\)

a)\(\dfrac{11}{42}=\dfrac{35}{42}\)

b) \(\dfrac{160}{28}=\dfrac{10}{28}\)

c) \(\dfrac{16}{60}=\dfrac{14}{60}\)

Bài 2:

a: \(\dfrac{12}{7}=\dfrac{12\cdot2}{7\cdot2}=\dfrac{24}{14};\dfrac{2}{2}=\dfrac{2\cdot7}{2\cdot7}=\dfrac{14}{14}\)

\(\dfrac{4}{7}=\dfrac{4\cdot2}{7\cdot2}=\dfrac{8}{14};\dfrac{9}{14}=\dfrac{9\cdot1}{14\cdot1}=\dfrac{9}{14}\)

mà \(\dfrac{24}{14}>\dfrac{14}{14}>\dfrac{9}{14}>\dfrac{8}{14}\)

nên \(\dfrac{12}{7}>\dfrac{2}{2}>\dfrac{9}{14}>\dfrac{4}{7}\)

b: \(\dfrac{2}{5}=\dfrac{2\cdot3}{5\cdot3}=\dfrac{6}{15};\dfrac{13}{15}=\dfrac{13\cdot1}{15\cdot1}=\dfrac{13}{15};\dfrac{19}{15}=\dfrac{19\cdot1}{15\cdot1}=\dfrac{19}{15}\)

\(\dfrac{2}{3}=\dfrac{2\cdot5}{3\cdot5}=\dfrac{10}{15}\)

mà \(\dfrac{19}{15}>\dfrac{13}{15}>\dfrac{10}{15}>\dfrac{6}{15}\)

nên \(\dfrac{19}{15}>\dfrac{13}{15}>\dfrac{2}{3}>\dfrac{2}{5}\)

c: \(\dfrac{2}{3}=\dfrac{2\cdot6}{3\cdot6}=\dfrac{12}{18};\dfrac{1}{2}=\dfrac{1\cdot9}{2\cdot9}=\dfrac{9}{18}\)

\(\dfrac{11}{18}=\dfrac{11}{18};\dfrac{5}{9}=\dfrac{5\cdot2}{9\cdot2}=\dfrac{10}{18}\)

mà \(\dfrac{12}{18}>\dfrac{11}{18}>\dfrac{10}{18}>\dfrac{9}{18}\)

nên \(\dfrac{2}{3}>\dfrac{11}{18}>\dfrac{5}{9}>\dfrac{1}{2}\)

d: \(\dfrac{1}{2}=\dfrac{1\cdot8}{2\cdot8}=\dfrac{8}{16};\dfrac{3}{8}=\dfrac{3\cdot2}{8\cdot2}=\dfrac{6}{16}\)

\(\dfrac{5}{4}=\dfrac{5\cdot4}{4\cdot4}=\dfrac{20}{16};\dfrac{7}{16}=\dfrac{7}{16}\)

mà \(\dfrac{20}{16}>\dfrac{8}{16}>\dfrac{7}{16}>\dfrac{6}{16}\)

nên \(\dfrac{5}{4}>\dfrac{1}{2}>\dfrac{7}{16}>\dfrac{3}{8}\)

e: \(\dfrac{13}{20}=\dfrac{13}{20};\dfrac{3}{5}=\dfrac{3\cdot4}{5\cdot4}=\dfrac{12}{20};\dfrac{7}{10}=\dfrac{7\cdot2}{10\cdot2}=\dfrac{14}{20}\)

\(\dfrac{1}{4}=\dfrac{1\cdot5}{4\cdot5}=\dfrac{5}{20}\)

mà \(\dfrac{14}{20}>\dfrac{13}{20}>\dfrac{12}{20}>\dfrac{5}{20}\)

nên  \(\dfrac{7}{10}>\dfrac{13}{20}>\dfrac{3}{5}>\dfrac{1}{4}\)

f: \(\dfrac{23}{28}=\dfrac{23\cdot1}{28\cdot1}=\dfrac{23}{28};\dfrac{9}{14}=\dfrac{9\cdot2}{14\cdot2}=\dfrac{18}{28}\)

\(\dfrac{3}{4}=\dfrac{3\cdot7}{4\cdot7}=\dfrac{21}{28};\dfrac{5}{7}=\dfrac{5\cdot4}{7\cdot4}=\dfrac{20}{28}\)

mà \(\dfrac{23}{28}>\dfrac{21}{28}>\dfrac{20}{28}>\dfrac{18}{28}\)

nên \(\dfrac{23}{28}>\dfrac{3}{4}>\dfrac{5}{7}>\dfrac{9}{14}\)

Bài 1 : 

\(\dfrac{14}{7}>\dfrac{9}{7}\)            \(\dfrac{6}{13}< 1\)          \(\dfrac{7}{9}=\dfrac{14}{18}\)          \(\dfrac{4}{9}< \dfrac{26}{45}\)

\(\dfrac{11}{24}>\dfrac{3}{8}\)            \(\dfrac{42}{91}< \dfrac{7}{13}\)       \(\dfrac{34}{64}< \dfrac{13}{16}\)          \(\dfrac{17}{30}>\dfrac{8}{15}\)

bài 2 

\(\dfrac{12}{17};\dfrac{2}{2};\dfrac{4}{7};\dfrac{9}{14}\)               \(\dfrac{19}{15};\dfrac{13}{15};\dfrac{2}{3};\dfrac{2}{5}\)                 \(\dfrac{2}{3};\dfrac{11}{18};\dfrac{5}{9};\dfrac{1}{2}\)

 \(\dfrac{5}{4};\dfrac{1}{2};\dfrac{7}{16};\dfrac{3}{8}\)               \(\dfrac{7}{10};\dfrac{13}{20};\dfrac{7}{10};\dfrac{1}{4}\)                 \(\dfrac{23}{18};\dfrac{3}{4};\dfrac{5}{7};\dfrac{9}{14}\)

bài 3

những phân số thuộc " ? " là \(\dfrac{7}{8};\dfrac{1}{2};\dfrac{27}{24};\dfrac{26}{16}\)

bài 4 

\(\dfrac{1}{4}=\dfrac{9}{36};\dfrac{2}{9}=\dfrac{8}{36}\)

\(\dfrac{5}{12}=\dfrac{15}{36};\dfrac{4}{36}\)

\(\Rightarrow\dfrac{15}{36}>\dfrac{9}{36}>\dfrac{8}{36}>\dfrac{4}{36}\)\(\Rightarrow\)ngọc là lớp trưởng

Bài 4:

\(\dfrac{1}{4}=\dfrac{1\cdot9}{4\cdot9}=\dfrac{9}{36};\dfrac{2}{9}=\dfrac{2\cdot4}{9\cdot4}=\dfrac{8}{36}\)

\(\dfrac{5}{12}=\dfrac{5\cdot3}{12\cdot3}=\dfrac{15}{36};\dfrac{4}{36}=\dfrac{4\cdot1}{36\cdot1}=\dfrac{4}{36}\)

Vì \(\dfrac{15}{36}>\dfrac{9}{36}>\dfrac{8}{36}>\dfrac{4}{36}\)

nên lớp trưởng sẽ là bạn Ngọc

\(\dfrac{14}{7}>\dfrac{9}{7}\)

\(\dfrac{6}{13}< 1\)

\(\dfrac{7}{9}=\dfrac{14}{18}\)

\(\dfrac{4}{9}=\dfrac{20}{45}< \dfrac{26}{45}\)

\(\dfrac{11}{24}>\dfrac{9}{24}=\dfrac{3}{8}\)

\(\dfrac{42}{91}=\dfrac{42:7}{91:7}=\dfrac{6}{13}< \dfrac{7}{13}\)

\(\dfrac{34}{64}< \dfrac{52}{64}=\dfrac{13}{16}\)

\(\dfrac{17}{30}>\dfrac{16}{30}=\dfrac{8}{15}\)

bài 2 

nối với 26,     7,    27

            ___  __   ___

           16       8      24

Bài 3:

Các phân số cần nối là 13/4; 26/16; 7/8

a.

các phân số bằng \(\dfrac{4}{5}\) là: \(\dfrac{8}{10};\dfrac{28}{25};\dfrac{32}{40}\)

b.

Các phân số bằng \(\dfrac{3}{7}\) là: \(\dfrac{27}{63};\dfrac{36}{84};\dfrac{15}{35}\)

2. C

1. A

Đáp án câu 1 là A

Đáp án câu 2 là C

B. 12/6

Chọn C

C nhé bạn

a: Các phân số tối giản là \(\dfrac{1}{3};\dfrac{4}{7};\dfrac{72}{73}\) vì ƯCLN(1;3)=1; ƯCLN(4;7)=1; ƯCLN(72;73)=1

b:

Các phân số rút gọn được là

 \(\dfrac{8}{12}=\dfrac{8:4}{12:4}=\dfrac{2}{3}\)

\(\dfrac{30}{36}=\dfrac{30:6}{36:6}=\dfrac{5}{6}\)