\(\frac{25}{50}+\frac{5}{15}=\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\)

\(\frac{72}{90}+\frac{7}{28}=\frac{8}{10}+\frac{1}{4}=\frac{32}{40}+\frac{10}{40}=\frac{42}{40}=\frac{21}{20}\)

\(\frac{32}{96}+\frac{8}{28}=\frac{1}{3}+\frac{2}{7}=\frac{7}{21}+\frac{6}{21}=\frac{13}{21}\)

1/2 + 1/3

1/2=1.3/2.3=3/6 : 1/3=1.2/3.2=2/6

3/6 + 2/6=5/6

a, \(\frac{25}{50}\)=    \(\frac{25:25}{50:25}\)=    \(\frac{1}{2}\)                   \(\frac{5}{15}\)=    \(\frac{5:5}{15:5}\)=    \(\frac{1}{3}\)

\(\frac{1}{2}\)+    \(\frac{1}{3}\)=    \(\frac{3}{6}\)+     \(\frac{2}{6}\)=    \(\frac{5}{6}\)

b, \(\frac{72}{90}\)=    \(\frac{72:18}{90:18}\)=    \(\frac{4}{5}\)                   \(\frac{7}{28}\)=    \(\frac{7:7}{28:7}\)=    \(\frac{1}{4}\)

\(\frac{4}{5}\)+    \(\frac{1}{4}\) =    \(\frac{16}{20}\)+    \(\frac{5}{20}\)=      \(\frac{21}{20}\)

c, \(\frac{32}{96}\)=    \(\frac{32:32}{96:32}\)=    \(\frac{1}{3}\)                    \(\frac{8}{28}\)=    \(\frac{8:4}{28:4}\)=    \(\frac{2}{7}\)

\(\frac{1}{3}\)+    \(\frac{2}{7}\)  =    \(\frac{7}{21}\)+    \(\frac{6}{21}\)=    \(\frac{13}{21}\)

Lời giải và hướng dẫn:

a) 25/50 + 5/15 = 1/2 + 1/3 = 3/6 + 2/6 = 5/6.

b) 72/90 + 7/28 = 4/5 + 1/4 = 16/20 + 5/20 = 21/20.

c) 32/96 + 8/28 = 1/3 + 2/7 = 7/21 + 6/21 = 13/21.

A)\(\frac{25}{50}+\frac{5}{15}\)

\(=\frac{1}{2}+\frac{1}{3}\)

\(=\frac{3+2}{6}\)\(=\frac{5}{6}\)

B)  \(\frac{72}{90}+\frac{7}{28}\)\(=\frac{4}{5}+\frac{1}{4}\)\(=\frac{16+5}{20}\)\(=\frac{21}{20}\)

C)\(\frac{32}{96}+\frac{8}{28}\)\(=\frac{1}{3}+\frac{2}{7}\)\(=\frac{7+6}{21}\)=\(\frac{13}{21}\)

NĂM MỚI VUI VẺ

20/50 + 5/15                72/90 + 7/28             32/96 + 8/28

= 2/5 + 1/3                 = 4/5 + 1/4               = 1/3 + 2/7

= 11/15                       = 21/20                    = 13/21

 \(\frac{20}{50}+\frac{5}{15}\\ =\frac{2}{5}+\frac{1}{3}\\ =\frac{6}{15}+\frac{5}{15}=\frac{11}{15}\)

a: =2/5+3/5=1

b: =1/3+2/3=1

c: =7/8+5/8=12/8=3/2

d: =2/7+3/7=5/7

\(a,\dfrac{2}{5}+\dfrac{3}{5}=\dfrac{5}{5}=1\\ b,\dfrac{1}{3}+\dfrac{2}{3}=\dfrac{3}{3}=1\\ c,\dfrac{7}{8}+\dfrac{5}{8}=\dfrac{12}{8}=\dfrac{3}{2}\\ d,\dfrac{1}{7}+\dfrac{3}{7}=\dfrac{4}{7}\)

a) 2/5+ 3/5= 5/5=1

b) 1/3+2/3=3/3=1

c) 7/8+5/8= 12/8=3/2

d) 2/7+3/7=5/7

\(\dfrac{4}{5}+\dfrac{1}{4}=\dfrac{21}{20}\)

=4/5+1/4=21/20

\(\dfrac{4}{5}+\dfrac{1}{4}=\dfrac{21}{20}\)

a.4/5+3/15 = 4/5+ 3/15:3=4/5+1/5=5/5

b.2/3+32/24=2/3+32/24:8=2/3+4/3=6/3

c.5/6+15/18=5/6x3+15/18=15/18+15/18=30/18

mn ơi e vít nhầm là tính rồi rút gọn mn sửa lại là rút gọn rùi tính

a: =2/5+3/5=1

b: =1/3+5/6=2/6+5/6=7/6

c: =7/8+5/8=12/8=3/2

d: =2/3+2/10

=20/30+6/30

=26/30=13/15

e: =1/2+1/3

=3/6+2/6

=5/6

f: =2/7+1/6

=12/42+7/42

=19/42

`2/5 + 9/15= 2/5 + 3/5=5/5=1`

`15/45 + 25/30= 1/3 + 5/6= 2/6+5/6=7/6`

`28/32 + 45/72=7/8+ 5/8=12/8=3/2`

`8/28 + 5/30= 2/7 + 1/6= 12/42 + 7/42= 19/42`