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a, 7\(\dfrac{3}{5}\) : \(x\) = 5\(\dfrac{4}{15}\) - 1\(\dfrac{1}{6}\)
\(\dfrac{38}{5}\) : \(x\) = \(\dfrac{79}{15}\) - \(\dfrac{7}{6}\)
\(x\) = \(\dfrac{41}{10}\)
\(x\) = \(\dfrac{38}{5}\) : \(\dfrac{41}{10}\)
\(x\) = \(\dfrac{76}{41}\)
b, \(x\) \(\times\) 2\(\dfrac{2}{3}\) = 3\(\dfrac{4}{8}\) + 6\(\dfrac{5}{12}\)
\(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{7}{2}\) + \(\dfrac{77}{12}\)
\(x\) \(\times\) \(\dfrac{8}{3}\) = \(\dfrac{119}{12}\)
\(x\) = \(\dfrac{119}{12}\)
\(x\) = \(\dfrac{119}{12}\): \(\dfrac{8}{3}\)
\(x\) = \(\dfrac{119}{32}\)
a) \(\frac{51}{3}-\frac{22}{3}=\frac{51-22}{3}=\frac{29}{3}\)
b) \(\frac{5}{12}+\frac{5}{6}-\frac{3}{4}=\frac{5}{12}+\frac{10}{12}-\frac{9}{12}=\frac{5+10-9}{12}=\frac{6}{12}=\frac{1}{2}\)
c) \(1-\left(\frac{1}{5}+\frac{1}{2}\right)=\frac{10}{10}-\frac{2}{10}-\frac{5}{10}=\frac{10-5-2}{10}=\frac{3}{10}\)
d) \(\frac{111}{4}-\left(\frac{25}{7}+\frac{51}{4}\right)=\frac{777}{28}-\frac{60}{28}-\frac{357}{28}=\frac{360}{28}=\frac{90}{7}\)
e) \(\left(\frac{85}{11}+\frac{35}{7}\right)-\frac{35}{11}=\left(\frac{85}{11}-\frac{35}{11}\right)+\frac{35}{7}=\frac{50}{11}-\frac{35}{7}=\frac{350}{77}-\frac{385}{77}=-\frac{35}{77}\)
(dấu . là dấu nhân )
a, \(\frac{3}{2}\cdot\frac{4}{7}+\frac{3}{7}\cdot\frac{3}{2}\)
= \(\frac{3}{2}\left(\frac{4}{7}+\frac{3}{7}\right)\)
=\(\frac{3}{2}\cdot\frac{7}{7}=\frac{3}{2}\)
b, \(\frac{12}{5}\cdot4-4\cdot\frac{7}{5}\)
=\(4\left(\frac{12}{5}-\frac{7}{5}\right)=4\cdot\frac{5}{5}=4\)
c, \(\frac{5}{11}:\frac{1}{2}+\frac{6}{11}:\frac{1}{2}\)
=\(2\left(\frac{5}{11}+\frac{6}{11}\right)=2\cdot\frac{11}{11}=2\)
a;3/2x(4/7+3/7)
=3/2x1
=3/2
b;12/5x4-4x7/5
=4x(12/5-7/5)
=4x1
=4
c;5/11:1/2+6/11:1/2
=1/2:(5/11+6/11)
=1/2:1
=1/2
`3/4 + 5/6 = 9/12 + 10/12 = 19/12`
`1/2 + 7/12 = 6/12 + 7/12 = 13/12`
`2/3 xx 3/4 = 2/4 = 1/2`
`7/4 : 2 = 7/4 xx 1/2 = 7/8`
\(a,\dfrac{3}{4}+\dfrac{5}{6}=\dfrac{18}{24}+\dfrac{20}{24}=\dfrac{38}{24}=\dfrac{19}{12}\)
\(b,\dfrac{1}{2}+\dfrac{7}{12}=\dfrac{6}{12}+\dfrac{7}{12}=\dfrac{13}{12}\)
\(c,\dfrac{2}{3}x\dfrac{3}{4}=\dfrac{2}{4}\)
\(d,\dfrac{7}{4}:2=\dfrac{7}{4}x\dfrac{1}{2}=\dfrac{7}{8}\)
1. a
\(\dfrac{8}{5}-\dfrac{5}{6}\cdot\dfrac{3}{4}\)
\(=\dfrac{8}{5}-\dfrac{5\cdot3}{3\cdot2\cdot4}\)
\(=\dfrac{8}{5}-\dfrac{5}{8}=\dfrac{39}{40}\)
1.b
\(=\dfrac{7}{8}+\dfrac{5}{6}\cdot\dfrac{3}{2}\)
\(=\dfrac{7}{8}+\dfrac{5\cdot3}{3\cdot2\cdot2}\)
\(=\dfrac{7}{8}+\dfrac{5}{4}=\dfrac{17}{8}\)
2.a
\(\dfrac{4}{5}+x=\dfrac{11}{10}\)
\(x=\dfrac{11}{10}-\dfrac{4}{5}=\dfrac{3}{10}\)
2.b
\(x-\dfrac{3}{4}=\dfrac{5}{7}\)
\(x=\dfrac{5}{7}+\dfrac{3}{4}=\dfrac{41}{28}\)
a,x/12-1/3=3/4
x/12 =3/4+1/3
x/12 =13/12
vậy x =13
b,3/4-x=5/12
x=3/4-5/12
x=4/12=1/3
c,x nhân 2/3-1/3=1/4
x nhân 2/3 =1/4+1/3
x nhân 2/3 =7/12
x =7/12 : 2/3
x =21/24=7/8
d,5/7-(x-1/2)=1/7
x-1/2 =5/7-1/7
x -1/2 =4/7
x =4/7+1/2
x =15/14
bạn nhớ k cho mình nhé!
\(\frac{2}{3}\)x \(\frac{5}{8}\)x \(\frac{8}{15}\)= \(\frac{2}{3}\)x \(\frac{1}{15}\)= \(\frac{2}{45}\)
\(\frac{22}{5}\)x \(12\)x \(\frac{20}{40}\)= \(\frac{22}{5}\)x \(12\)x \(\frac{1}{2}\)= \(\frac{22}{5}\)x 6 = \(\frac{122}{5}\)
\(\frac{7}{2}\)x \(\frac{26}{7}\)x \(\frac{4}{13}\)= \(\frac{91}{7}\)x \(\frac{4}{13}\)
1.3.77−1+3.7.99−3+7.9.1313−7+9.13.1515−9+\frac{19-13}{13.15.19}+13.15.1919−13
=\frac{1}{1.3}-\frac{1}{3.7}+\frac{1}{3.7}-\frac{1}{7.9}+\frac{1}{7.9}-\frac{1}{9.13}+\frac{1}{9.13}-\frac{1}{13.15}+\frac{1}{13.15}-\frac{1}{15.19}=1.31−3.71+3.71−7.91+7.91−9.131+9.131−13.151+13.151−15.191
=\frac{1}{1.3}-\frac{1}{15.19}=\frac{95}{285}-\frac{1}{285}=\frac{94}{285}=1.31−15.191=28595−2851=28594
b,=\frac{1}{6}.\left(\frac{6}{1.3.7}+\frac{6}{3.7.9}+\frac{6}{7.9.13}+\frac{6}{9.13.15}+\frac{6}{13.15.19}\right)b,=61.(1.3.76+3.7.96+7.9.136+9.13.156+13.15.196)
làm giống như trên
c,=\frac{1}{8}.\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+...+\frac{1}{48.49.50}\right)c,=81.(1.2.31+2.3.41+3.4.51+...+48.49.501)
=\frac{1}{16}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+\frac{2}{3.4.5}+...+\frac{2}{48.49.50}\right)=161.(1.2.32+2.3.42+3.4.52+...+48.49.502)
=\frac{1}{16}.\left(\frac{3-1}{1.2.3}+\frac{4-2}{2.3.4}+\frac{5-3}{3.4.5}+...+\frac{50-48}{48.49.50}\right)=161.(1.2.33−1+2.3.44−2+3.4.55−3+...+48.49.5050−48)
=\frac{1}{16}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+...+\frac{1}{48.49}-\frac{1}{49.50}\right)=161.(1.21−2.31+2.31−3.41+3.41−4.51+...+48.491−49.501)
=\frac{1}{16}.\left(\frac{1}{2}-\frac{1}{2450}\right)=\frac{1}{16}.\left(\frac{1225}{2450}-\frac{1}{2450}\right)=\frac{153}{4900}=161.(21−24501)=161.(24501225−24501)=4900153
d,=\frac{5}{7}.\left(\frac{7}{1.5.8}+\frac{7}{5.8.12}+\frac{7}{8.12.15}+...+\frac{7}{33.36.40}\right)d,=75.(1.5.87+5.8.127+8.12.157+...+33.36.407)
=\frac{5}{7}.\left(\frac{8-1}{1.5.8}+\frac{12-5}{5.8.12}+\frac{15-8}{8.12.15}+...+\frac{40-33}{33.36.40}\right)=75.(1.5.88−1+5.8.1212−5+8.12.1515−8+...+33.36.4040−33)
=\frac{5}{7}.\left(\frac{1}{1.5}-\frac{1}{5.8}+\frac{1}{5.8}-\frac{1}{8.12}+\frac{1}{8.12}-\frac{1}{12.15}+...+\frac{1}{33.36}-\frac{1}{36.40}\right)=75.(1.51−5.81+5.81−8.121+8.121−12.151+...+33.361−36.401)
=\frac{5}{7}.\left(\frac{1}{5}-\frac{1}{1440}\right)=\frac{5}{7}.\left(\frac{288}{1440}-\frac{1}{1440}\right)=\frac{41}{288}=75.(51−14401)=75.(1440288−14401)=28841
P/S: . là nhân nha
4/5+6=4/5+30/5=34/5
1/2+1/3+7/12=6/12+4/12+7/12=17/12
3/4-5/12=9/12-5/12=4/12
2/3:4/3*5=1/2*5=1/2*5/1=5/2