Hỗn số

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, \(x+\dfrac{16}{5}=4\)

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

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

\(a,4\dfrac{1}{4}-2=\dfrac{17}{4}-2=\dfrac{9}{4};\dfrac{5}{8}+2\dfrac{3}{5}=\dfrac{5}{8}+\dfrac{13}{5}=\dfrac{129}{40}\\ b,4\dfrac{4}{9}:2=\dfrac{40}{9}\cdot\dfrac{1}{2}=\dfrac{20}{9};\dfrac{2}{3}+3\dfrac{1}{6}=\dfrac{2}{3}+\dfrac{19}{6}=\dfrac{23}{6}\\ c,3\dfrac{1}{5}+2=\dfrac{9}{5}+2=\dfrac{19}{5};\dfrac{3}{5}-2\dfrac{4}{5}=\dfrac{3}{5}-\dfrac{14}{5}=-\dfrac{11}{5}\)

\(d,5\dfrac{1}{7}-2=\dfrac{36}{7}-2=\dfrac{22}{7};\dfrac{4}{5}:1\dfrac{1}{5}=\dfrac{4}{5}:\dfrac{6}{5}=\dfrac{2}{3}\\ e,2\dfrac{3}{5}+1=\dfrac{13}{5}+1=\dfrac{18}{5};\dfrac{1}{4}\cdot2\dfrac{2}{3}=\dfrac{1}{4}\cdot\dfrac{8}{3}=\dfrac{2}{3}\\ f,4\dfrac{1}{3}\cdot1=\dfrac{13}{3};\dfrac{1}{2}+5\dfrac{2}{7}=\dfrac{1}{2}+\dfrac{37}{7}=\dfrac{81}{14}\)

\(40.\)

\(a\)) \(S\)

\(b\)) Đ

\(c\)) Đ

\(d\)) \(S\)

\(41.\)

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

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

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

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

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

\(1\dfrac{1}{2}x1\dfrac{1}{3}x1\dfrac{1}{4}x1\dfrac{1}{5}x1\dfrac{1}{6}x1\dfrac{1}{7}x1\dfrac{1}{8}x1\dfrac{1}{9}\)

\(=\dfrac{3}{2}x\dfrac{4}{3}x\dfrac{5}{4}x\dfrac{6}{5}x\dfrac{7}{6}x\dfrac{8}{7}x\dfrac{9}{8}x\dfrac{10}{9}\)

\(=x^7.\dfrac{3.4.5.6.7.8.9.10}{2.3.4.5.6.7.8.9}\)

\(=x^7.\dfrac{10}{2}\)

\(=5x^7\)

\(=\dfrac{3}{2}\times\dfrac{4}{3}\times\dfrac{5}{4}\times...\times\dfrac{9}{8}\times\dfrac{10}{9}=\dfrac{10}{2}=5\)

a)83/12

b)255/14

Đáp án:

a) \(\dfrac{83}{12}\)

b) \(\dfrac{255}{14}\)

Hok tốt

= 17

16,17 < x < 17,22

số tự nhiên x thỏa mãn là 17 vì 16,17 < 17 < 17,22

vậy x là 17

17

n = 7 nhé bạn 

34,2:5=6.84                                                                          2,45x5=12.25

  Vậy 6.84<n<12.25 nên n là:[7;8;9;10;11;12] vì đề bài yêu cầu n là số tự nhiên nhỏ nhất nên n=7

\(\dfrac{887}{35}\)

= \(\dfrac{11}{5}+\dfrac{22}{7}=\dfrac{77}{35}+\dfrac{110}{35}=\dfrac{187}{35}\)

=77/35+110/35

=(77+110)/35

=187/35