Hỗn số

\(\dfrac{2}{5}+\dfrac{3}{7}\)
 

\(=\dfrac{14}{35}+\dfrac{15}{35}\)
 

\(=\dfrac{29}{35}\)

\(3+\dfrac{2}{5}\)
 

\(=\dfrac{15}{5}+\dfrac{2}{5}\)
 

\(=\dfrac{17}{5}\)

\(\dfrac{5}{7}-\dfrac{1}{6}\)
 

\(=\dfrac{30}{42}-\dfrac{7}{42}\)
 

\(=\dfrac{23}{42}\)

\(\dfrac{14}{3}-3\)

\(=\dfrac{14}{3}-\dfrac{9}{3}\)
 

\(=\dfrac{5}{3}\)

\(\dfrac{5}{6}\times\dfrac{4}{3}\)
 

\(=\dfrac{20}{18}\)  \(=\dfrac{10}{9}\)

\(5\times\dfrac{8}{15}\)
 

\(=\dfrac{40}{15}\) \(=\dfrac{8}{3}\)

\(\dfrac{4}{9}:5\)

\(=\dfrac{4}{9}\times\dfrac{1}{5}\)
 

\(=\dfrac{4}{45}\)

\(\dfrac{6}{5}:\dfrac{5}{6}\)
 

\(=\dfrac{6}{5}\times\dfrac{6}{5}\)
 

\(=\dfrac{36}{25}\)

\(1\dfrac{1}{5}+1\dfrac{2}{4}=\dfrac{6}{5}+\dfrac{6}{4}=\dfrac{24}{20}+\dfrac{30}{20}=\dfrac{54}{40}\)

Cách chuyển hỗn số thành phân số :

\(1\dfrac{1}{5}=\dfrac{1x5+1}{5}=\dfrac{6}{5}\)

\(1\dfrac{2}{4}=\dfrac{1x4+2}{4}\dfrac{6}{4}\)

\(1\dfrac{1}{5}+1\dfrac{2}{4}=\dfrac{6}{5}+\dfrac{3}{2}=\dfrac{6\times2}{5\times2}+\dfrac{3\times5}{2\times5}=\dfrac{12}{10}+\dfrac{15}{10}=\dfrac{12+15}{10}=\dfrac{27}{10}.\)

\(3\dfrac{2}{7} : 1\dfrac{4}{7}=\dfrac{23}{7} : \dfrac{11}{7}=\dfrac{23}{7} . \dfrac{7}{11}=\dfrac{23}{11}=2\dfrac{1}{11}\)

`3 2/7 : 1 4/7`

`=(3xx7+2)/7 : (1xx7+4)/7`

`=23/7 : 11/7`

`=23/7 xx 7/11`

`=23/11`

Bánh xe đó quay đc: \(1\dfrac{1}{3}.7\dfrac{1}{2}=7\dfrac{1}{6}\)  (vòng)

9m 7dm = 9m + \(\dfrac{7}{10}m=9\dfrac{7}{10}m\) 

11cm 3mm = 11cm + \(\dfrac{3}{10}cm=11\dfrac{3}{10}cm\)

1m 85cm = 1m + \(\dfrac{17}{20}m=1\dfrac{17}{20}m\)

6m 6cm = 6m + \(\dfrac{3}{50}m=6\dfrac{3}{50}\)m

`2 1/2`

\(\text{2}\dfrac{\text{1}}{2}\)

\(\dfrac{5}{6}\)

x+\(3\dfrac{1}{5}\)=4

x=4-\(3\dfrac{1}{5}\)

x=\(\dfrac{4}{5}\)

\(x+3\dfrac{1}{5}=4\)

\(x+\dfrac{16}{5}=4\)

          \(x=4-\dfrac{16}{5}\)

          \(x=\dfrac{4}{5}\)

a, \(x+\dfrac{16}{5}=4\)

\(x=4-\dfrac{16}{5}\)

\(\Rightarrow x=\dfrac{4}{5}\)

\(40.\)

\(a\)) \(S\)

\(b\)) Đ

\(c\)) Đ

\(d\)) \(S\)

\(41.\)

\(a\)) \(1\dfrac{1}{3}+2\dfrac{1}{2}=\dfrac{4}{3}+\dfrac{5}{2}=\dfrac{23}{6}\)

\(b\)) \(3\dfrac{2}{5}-1\dfrac{1}{10}=\dfrac{17}{5}-\dfrac{11}{10}=\dfrac{23}{10}\)

\(c\)) \(3\dfrac{1}{2}.1\dfrac{1}{7}=\dfrac{7}{2}.\dfrac{8}{7}=\dfrac{56}{14}=4\)

\(d\)) \(4\dfrac{1}{6}:2\dfrac{1}{3}=\dfrac{25}{6}:\dfrac{7}{3}=\dfrac{25}{14}\)

a)83/12

b)255/14

Đáp án:

a) \(\dfrac{83}{12}\)

b) \(\dfrac{255}{14}\)

Hok tốt

\(\dfrac{3}{4}+1\dfrac{5}{6}=\dfrac{3}{4}+\dfrac{11}{6}=\dfrac{9}{12}+\dfrac{22}{12}=\dfrac{31}{12}\)

=3/4+11/6=31/12

3/4 + 11/6= 31/12