a, 48/64 + 7/4 

 = 3/4 + 7/4

 = 10/4

b, 3/8 + 119/56

= 3/8 + 17/8

= 20/8

a)48/64=3/4

3/4+7/4=10/4=5/2

b) 119/56=119:7/56:7=17/8

3/8+17/8=20/8=5/2

k mk nghen ^.-

\(a,\) \(\frac{48}{64}+\frac{7}{4}=\frac{3}{4}+\frac{7}{4}=\frac{5}{2}\) 

\(b,\)  \(\frac{3}{8}+\frac{119}{56}=\frac{3}{8}+\frac{17}{8}=\frac{5}{2}\)               

\(HAI\) \(\text{Đ}\text{ÁP}\) \(\text{ÁN}\) \(v\text{er}y\) \(...\) 

2 - 5 6 + 3 - 2 8 = 2 . - 5 3 2 + 3 . - 2 4 2 = 2 . - 5 3 + 3 . - 2 4 = 2 . - 125 + 3 . 16 = 2 . 125 + 3 . 16 = 298

Hướng dẫn giải:

b)15/25+6/21=3/5+2/7=31/35 nha bạn

a, \(\frac{5}{16}+\frac{3}{8}=\frac{5}{16}+\frac{6}{16}=\frac{11}{16}\)

b, \(\frac{15}{25}+\frac{6}{21}=\frac{3}{5}+\frac{2}{7}\)

                           \(=\frac{21}{35}+\frac{10}{35}=\frac{31}{35}\)

a) Ta có: \(\frac{5}{16}+\frac{3}{8}=\frac{5}{16}+\frac{6}{16}=\frac{11}{16}\)

b) Ta có: \(\frac{3}{5}+\frac{2}{7}=\frac{21}{35}+\frac{10}{35}=\frac{31}{35}\)

\(\dfrac{6}{36}+\dfrac{5}{6}=\dfrac{1}{6}+\dfrac{5}{6}=\dfrac{6}{6}=1\\ \dfrac{1}{4}+\dfrac{5}{30}=\dfrac{1}{4}+\dfrac{1}{6}=\dfrac{6}{24}+\dfrac{4}{24}=\dfrac{10}{24}=\dfrac{5}{12}\\ \dfrac{5}{56}+\dfrac{3}{21}=\dfrac{5}{56}+\dfrac{1}{7}=\dfrac{5}{56}+\dfrac{8}{56}=\dfrac{13}{56}\\\dfrac{12}{18}+\dfrac{12}{42}=\dfrac{2}{3}+\dfrac{2}{7}=\dfrac{14}{21}+\dfrac{6}{21}=\dfrac{20}{21} \)

6/36 + 5/6=1/6+5/6=6/6=1

1/4 + 5/30=1/4+1/6=6/24+4/24=10/24=5/12

5/56 + 3/21=5/56=1/7=5/56+8/56=13/56

12/18 + 12/42=2/3+2/7=14/21+6/21=20/21

\(a,\dfrac{6}{36}+\dfrac{5}{6}=\dfrac{1}{6}+\dfrac{5}{6}=\dfrac{6}{6}=1\\ b,\dfrac{1}{4}+\dfrac{5}{30}=\dfrac{1}{4}+\dfrac{1}{6}=\dfrac{6}{24}+\dfrac{4}{24}=\dfrac{5}{12}\\ c,\dfrac{5}{56}+\dfrac{3}{21}=\dfrac{5}{56}+\dfrac{8}{56}=\dfrac{13}{56}\\ d,\dfrac{12}{18}+\dfrac{12}{42}=\dfrac{14}{21}+\dfrac{6}{21}=\dfrac{20}{21}\)

7 5 - 5 6 + 1 3 =  42 30 - 25 30 + 1 3

= 17 30 + 1 3 = 17 10 + 10 30 = 27 30 = 9 10

Đáp án cần chọn là D

2/7 / 1/7 = 10/28 = 5/14

3/8 / 9/4 = 12/72 = 2/12

8/21 / 4/7 = 56/84 = 14/21

5/8 / 15 / 8 = 1/24 / 8 = 1/192

a: 78/42-4/7=13/7-4/7=9/7

100/110-56/88=10/11-7/11=3/11

75/35-11/7+21/49=15/7-11/7+3/7=7/7=1

99/72-15/40-1212/1616=11/8-3/8-3/4=1-3/4=1/4