a) 3 và 3/4=3,75
b) 19 và 3/8=19,375
c) 27 và 2/5=27,4
 

Bài 1:a,  \(\dfrac{13}{2}\) = \(\dfrac{13\times5}{2\times5}\) = \(\dfrac{65}{10}\)

          b, \(\dfrac{11}{40}\) = \(\dfrac{11\times25}{40\times25}\) = \(\dfrac{275}{1000}\)

         c, \(\dfrac{21}{250}\) = \(\dfrac{21\times4}{250\times4}\) = \(\dfrac{84}{1000}\)

         d, \(\dfrac{27}{45}\) = \(\dfrac{27:9}{45:9}\) = \(\dfrac{3}{5}\) = \(\dfrac{3\times2}{5\times2}\) = \(\dfrac{6}{10}\)

Bài 2:

a, (3\(\dfrac{1}{8}\) + 1\(\dfrac{3}{4}\)): 2\(\dfrac{1}{4}\)

= (\(\dfrac{25}{8}\) + \(\dfrac{7}{4}\)): \(\dfrac{9}{4}\)

= \(\dfrac{39}{8}\) \(\times\) \(\dfrac{4}{9}\)

= \(\dfrac{13}{6}\)

a) \(\frac{15}{10}=1,5\)        \(\frac{675}{10}=6,75\)          \(\frac{7}{10}=0,7\)      

\(\frac{79}{100}=0,79\)       \(\frac{5}{100}=0,05\)           \(\frac{67}{100}=0,67\)

b) \(\frac{1}{2}=1\div2=0,5\)                   \(\frac{3}{4}=3\div4=0,75\)

\(\frac{15}{8}=15\div8=1,875\)              \(\frac{7}{25}=7\div25=0,28\)

\(\frac{19}{30}=19\div30=0,63\)              \(\frac{21}{125}=21\div125=0,168\)

4\(\dfrac{1}{2}\)=4,5      3\(\dfrac{4}{5}\)=3,8         2\(\dfrac{3}{4}\)=2,75      1\(\dfrac{12}{25}\)=1,48.

4 1/2=4,5

3 4/5=3,8

2 3/4=2,75

1 12/25=1,48

đúng 100% nha

1/4 = 25/100 = 0,25

5/2 = 25/10 = 2,5

13/8 = 1625/1000 = 1,625

250/500 = 500/1000 = 0,5

46/200 = 23/100 = 0,23

13/4 = 325/100 = 3,25

27/300=0,09

3/8=0,375

\(\frac{27}{300}=0,09\)

\(\frac{3}{8}=0,375\)

0,7=7/10

0,05=1/20

0,079=79/1000

0,654=327/500

0,47=47/100

b)45/10=4,5

437/10=43,7

58246/100=58,246

94/100=0,94

53/1000=0,053

0,7=7/10

0,05=1/20

0,079=79/1000

0,654=327/500

0,47=47/100

b)45/10=4,5

437/10=43,7

58246/100=58,246

94/100=0,94

53/1000=0,053

4\(\dfrac{1}{2}\) = 4+0,5 = 4,5

4\(\dfrac{1}{2}\) = \(\dfrac{9}{2}\) = 4,5

3\(\dfrac{4}{5}\) = 3+0,8 = 3,8

3\(\dfrac{4}{5}\) = \(\dfrac{19}{5}\) = 3,8

2\(\dfrac{3}{4}\) = 2 + 0,75 = 2,75

2\(\dfrac{3}{4}\) = \(\dfrac{11}{4}\) = 2,75

1\(\dfrac{12}{25}\) = 1 + \(0,48\) = 1,48

1\(\dfrac{12}{25}\) = \(\dfrac{37}{25}\) = 1,48

4$\genfrac{}{}{0ex}{}{1}{2}$ = 4+0,5 = 4,5

4$\genfrac{}{}{0ex}{}{1}{2}$ = $\genfrac{}{}{0ex}{}{9}{2}$ = 4,5

3$\genfrac{}{}{0ex}{}{4}{5}$ = 3+0,8 = 3,8

3$\genfrac{}{}{0ex}{}{4}{5}$ = $\genfrac{}{}{0ex}{}{19}{5}$ = 3,8

2$\genfrac{}{}{0ex}{}{3}{4}$ = 2 + 0,75 = 2,75

2$\genfrac{}{}{0ex}{}{3}{4}$ = $\genfrac{}{}{0ex}{}{11}{4}$ = 2,75

1$\genfrac{}{}{0ex}{}{12}{25}$ = 1 + $0,48$ = 1,48

1$\genfrac{}{}{0ex}{}{12}{25}$ = $\genfrac{}{}{0ex}{}{37}{25}$ 

\(2\dfrac{3}{5}\) = 2 + 0,6 = 2,6

\(7\dfrac{1}{4}\) = 7 + 0,25 = 7,25

\(5\dfrac{1}{10}\) = 5 + 0,1 = 5,1

\(6\dfrac{1}{2}\) = 6 + 0,5 = 6,5