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1/2 + 1/3 + 1/4 = 6/12 + 4/12 + 3/12 = 13/12
2/3 + 3/4 + 4/5 = 8/12 + 9/12 + 4/5 = 17/12 + 4/5 = 85 / 60 + 48 / 60 = 133/ 60
6/5 + 4/3 + 7/9 = 18/ 15 + 20/15 + 7/9 = 38 /15 + 7/ 9 = 114/45 +35/45 = 149/45
8/9 - 5/6 = 16/18 - 15/18 = 1/18
15/17 - 11 /13 = 195/221 -187/221= 8/221
a) \(\frac{1}{2}+\frac{1}{3}+\frac{1}{4}\)
= \(\frac{6}{12}+\frac{4}{12}+\frac{3}{12}\)
= \(\frac{13}{12}\).
b) \(\frac{2}{3}+\frac{3}{4}+\frac{4}{5}\)
= \(\frac{8}{12}+\frac{9}{12}+\frac{4}{5}\)
= \(\frac{17}{12}+\frac{4}{5}\)
= \(\frac{85}{60}+\frac{48}{60}\)
= \(\frac{133}{60}\).
c)\(\frac{6}{5}+\frac{4}{3}+\frac{7}{9}\)
= \(\frac{54}{45}+\frac{62}{45}+\frac{35}{45}\)
= \(\frac{151}{45}\).
d) \(\frac{8}{9}-\frac{5}{6}\)
= \(\frac{16}{18}-\frac{15}{18}\)
= \(\frac{1}{18}\).
e) \(\frac{15}{17}-\frac{11}{13}\)
= \(\frac{195}{221}\)\(-\frac{187}{221}\)
= \(\frac{8}{221}\).
b)0,5x+2/3x+2/3=7/2
1/2x+2/3x+2/3=7/2
x(1/2+2/3)+2/3=7/12
x.7/6+2/3 =7/12
x.7/6 =7/12-2/3
x.7/6 =-1/12
x =-1/12:7/6
x =-1/14
b)3/5-2/15:x=1/2
2/15:x =3/5-1/2
2/15:x =1/10
x =2/15:1/10
x = 4/3
a) Vì 4 < 5 nên \(\frac{3}{4}>\frac{3}{5}\)
b) Vì 4 < 5 nên \(\frac{4}{7}< \frac{5}{7}\)
c) Ta có :
\(\frac{2}{7}=\frac{2\times5}{7\times5}=\frac{10}{35}\)
\(\frac{4}{5}=\frac{4\times7}{5\times7}=\frac{28}{35}\)
Vì 10 < 28 nên \(\frac{10}{35}< \frac{28}{35}\)hay \(\frac{2}{7}< \frac{4}{5}\)
d) Ta có :
\(\frac{8}{9}=\frac{8\times10}{9\times10}=\frac{80}{90}\)
\(\frac{9}{10}=\frac{9\times9}{10\times9}=\frac{81}{90}\)
Vì 80 < 81 nên \(\frac{80}{90}< \frac{81}{90}\)hay \(\frac{8}{9}< \frac{9}{10}\)
e) Ta có :
\(\frac{10}{9}=\frac{10\times2}{9\times2}=\frac{20}{18}\)
Vì 19 < 20 nên \(\frac{19}{18}< \frac{20}{18}\)hay \(\frac{19}{18}< \frac{10}{9}\)
f) Ta có :
\(\frac{8}{3}=\frac{8\times4}{3\times4}=\frac{32}{12}\)
\(\frac{5}{6}=\frac{5\times2}{6\times2}=\frac{10}{12}\)
Vì 32 > 10 nên \(\frac{32}{12}>\frac{10}{12}\)hay \(\frac{8}{3}>\frac{5}{6}\)
a) \(\frac{7}{28}\)=\(\frac{1}{4}\)
b) \(\frac{5}{3}\)=\(\frac{15}{9}\)
c) \(\frac{4}{5}\)+\(\frac{3}{5}\)=\(\frac{49}{35}\)
nha
a) 930 + 257 . 5 - 405 : 9
= 930 + 1285 - 45
= 2215 - 45
= 2170
b) ( 857 + 936 ) . 15 - 92 . 30
= 1793 . 15 - 92 . 30
= 26895 - 2760
= 24135
c) 1/5 + 5/3 = 28/15
d) 3/4 + 9/3 - 1/4 = 7/2
e) 3/4 + 1 1 /2 + 0,5 : 5/12
= 3/4 + 3/2 + 6/5
= 69/20
hok tốt
a. 930 + 257 . 5 - 405 : 9
= 930 + 1285 - 45
= 2215 - 45
= 2170
b. (857 +936 ) . 15 - 92 . 30
= 1793 . 15 - 2760
= 26895 - 2760
= 24135
c. \(\frac{1}{5}+\frac{5}{3}\)
= \(\frac{3}{15}+\frac{25}{15}\)
= \(\frac{28}{15}\)
d. \(\frac{3}{4}+\frac{9}{3}-\frac{1}{4}\)
= \(\frac{9}{12}+\frac{36}{12}-\frac{3}{12}\)
= \(\frac{42}{12}=\frac{7}{2}\)
e.\(\frac{3}{4}+1\frac{1}{2}+0,5:\frac{5}{12}\)
= \(\frac{3}{4}+\frac{3}{2}+\frac{6}{5}\)
= \(\frac{15}{20}+\frac{30}{20}+\frac{24}{20}\)
= \(\frac{69}{20}\)