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\(\dfrac{3}{5}+\dfrac{7}{8}=\dfrac{3.8+7.5}{5.8}=\dfrac{24+35}{40}=\dfrac{59}{40}\\ 2+\dfrac{3}{4}=\dfrac{2.4+3}{4}=\dfrac{11}{4}\\ 1-\dfrac{3}{4}=\dfrac{4-3}{4}=\dfrac{1}{4}\\\dfrac{6}{8}+7=\dfrac{6+7.8}{8}=\dfrac{62}{8}=\dfrac{31}{4}\\ \dfrac{35}{9}-2=\dfrac{35-2.9}{9}=\dfrac{17}{9}\)
Giải thích : \(\left(.\right)\) dấu chấm này là dấu nhân nhé
3/5+4/6=3/5+2/3=9/15+10/15=19/15
7-1/3=20/3
5x3/8=15/8
12/35:2/5=12/35x5/2=60/70=6/7
\(\dfrac{3}{5}+\dfrac{4}{6}=\dfrac{3}{5}+\dfrac{2}{3}=\dfrac{19}{15}\)
\(7-\dfrac{1}{3}=\dfrac{20}{3}\)
\(5x\dfrac{3}{8}=\dfrac{15}{8}\)
\(\dfrac{12}{35}:\dfrac{2}{5}=\dfrac{12}{35}x\dfrac{5}{2}=\dfrac{6}{7}\)
a) (27 -18) : 3 =?
Cách 1: (27 -18) : 3
= 9 : 3 = 3
Cách 2:(27 -18) : 3
= 27 : 3 - 18 : 3
= 9 - 6 = 3
b) (64 - 32) : 8 = ?
Cách 1:(64 - 32) : 8
= 32 : 8 = 4
Cách 2:(64 - 32) : 8
= 64 : 8 - 32 : 8
= 8 - 4 = 4
Nói thêm: Khi chia một hiệu cho một số, ta có thể chia số bị trừ và số trừ cho số đó (nếu chia hết), rồi trừ hai kết quả cho nhau.
(27 -18) : 3
= 27 : 3 - 18 : 3
`1/3 + 1/5 -1/4`
`= 5/15 + 3/15 -1/4`
`= 8/15 -1/4`
`= 17/60`
__
`7/8 -(1/4 + 2/5)`
`= 7/8-1/4 - 2/5`
`= 7/8 - 2/8 -2/5`
`= 5/8 -2/5`
`= 9/40`
__
`5/11-(3/5 -6/11)`
`= 5/11 -3/5 +6/11`
`= (5/11 + 6/11)-3/5`
`= 1 -3/5`
`= 5/5-3/5`
`=2/5`
__
`5/7 - ( 19/35 - 6/15)`
`= 5/7 - 19/35 + 6/15`
`= 25/35 -19/35 + 6/15`
`=6/35 +6/15`
`=4/7`
\(3+\frac{35}{21}+6=\frac{3}{1}+\frac{35}{21}+\frac{6}{1}=\frac{63}{21}+\frac{35}{21}+\frac{126}{21}=\frac{224}{21}\)
\(\frac{3}{8}+\frac{1}{5}+7=\frac{3}{8}+\frac{1}{5}+\frac{7}{1}=\frac{15}{40}+\frac{8}{40}+\frac{280}{40}=\frac{303}{40}\)
\(\frac{14}{28}+\frac{3}{4}+2=\frac{2}{4}+\frac{3}{4}+2=\frac{2}{4}+\frac{3}{4}+\frac{2}{1}=\frac{2}{4}+\frac{3}{4}+\frac{8}{4}=\frac{13}{4}\)
\(\frac{3}{5}+\frac{1}{4}+\frac{2}{3}=\frac{36}{60}+\frac{15}{60}+\frac{40}{60}=\frac{91}{60}\)
a) \(6-\dfrac{2}{5}+\dfrac{3}{5}\) x \(3\)
\(=6-\dfrac{2}{5}+\dfrac{9}{5}\)
\(=\dfrac{30}{5}-\dfrac{2}{5}+\dfrac{9}{5}\)
\(=\dfrac{30-2+9}{5}=\dfrac{37}{5}\)
b) \(\left(\dfrac{31}{35}-\dfrac{4}{7}\right)\) x \(\dfrac{8}{7}:2\)
\(=\left(\dfrac{31}{35}-\dfrac{20}{35}\right)\) x \(\dfrac{8}{7}:2\)
\(=\dfrac{11}{35}\) x \(\dfrac{8}{7}:2\)
\(=\dfrac{11}{35}\) x \(\dfrac{8}{7}\) x \(\dfrac{1}{2}\)
\(=\dfrac{\text{11 x 8 x 1}}{\text{ 35 x 7 x 2}}=\dfrac{88}{490}=\dfrac{88}{245}\)
a) 6−25+356−25+35 x 33
=6−25+95=6−25+95
=305−25+95=305−25+95
=30−2+95=375=30−2+95=375
b) (3135−47)(3135−47) x 87:287:2
=(3135−2035)=(3135−2035) x 87:287:2
=1135=1135 x 8
a) (15 +35) : 5 = ?
Cách 1: (15 +35) : 5
= 50 : 5 = 10
Cách 2: (15 +35) : 5
= 15 : 5 + 35 : 5
= 3 + 7 = 10
+) (80 +4) : 4 = ?
Cách 1:(80 +4) : 4
= 84 : 4 = 21
Cách 2:(80 +4) : 4
= 80 : 4 + 4 :4 = 20 +1 = 21
b) 18 : 6 + 24 : 6 = ?
Cách 1: 18 : 6 + 24 : 6
= 3 + 4 = 7
Cách 2: (18 + 24) : 6
= 42 : 6 = 7
+) 60 : 3 + 9 : 3 =?
Cách 1: 60 : 3 + 9 : 3
= 20 + 3 = 23
Cách 2: 60 : 3 + 9 : 3
=(60 +9) : 3 = 23
a) (15 +35) : 5 = ?
Cách 1: (15 +35) : 5
= 50 : 5 = 10
Cách 2: (15 +35) : 5
= 15 : 5 + 35 : 5
= 3 + 7 = 10
+) (80 +4) : 4 = ?
Cách 1:(80 +4) : 4
= 84 : 4 = 21
Cách 2:(80 +4) : 4
= 80 : 4 + 4 :4 = 20 +1 = 21
b) 18 : 6 + 24 : 6 = ?
Cách 1: 18 : 6 + 24 : 6
= 3 + 4 = 7
Cách 2: (18 + 24) : 6
= 42 : 6 = 7
+) 60 : 3 + 9 : 3 =?
Cách 1: 60 : 3 + 9 : 3
= 20 + 3 = 23
Cách 2: 60 : 3 + 9 : 3
=(60 +9) : 3 = 23
HT\(\frac{6-2}{5}+\frac{3}{5.3}\)
\(=\frac{4}{5}+\frac{1}{5.1}\)
\(=\frac{4}{5}+\frac{1}{5}\)
\(=\frac{5}{5}=1\)
a. 6 x 3 - ( \(\frac{2}{5}+\frac{3}{5}\)) = 6 x 3 - \(\frac{5}{5}\)= 6 x 3 - 1 = 18 - 1 = 17
b.( \(\frac{31}{35}-\frac{4}{7}\)) x \(\frac{8}{7}\): 2 =\(\frac{11}{35}\)x \(\frac{8}{7}\): 2 =\(\frac{88}{245}\): 2 = \(\frac{88}{490}\)= \(\frac{44}{245}\)= ...........rút gọn đến khi hết
a) \(6-\frac{2}{5}+\frac{3}{5}\times3\)
\(=6-\frac{2}{5}+\frac{9}{5}\)
\(=\frac{30}{5}-\frac{2}{5}+\frac{9}{5}\)
\(=\frac{28}{5}+\frac{9}{5}\)
\(=\frac{37}{5}\)
b) \(\left(\frac{31}{35}-\frac{4}{7}\right)\times\frac{8}{7}:2\)
\(=\frac{11}{35}\times\frac{8}{7}:2\)
\(=\frac{88}{245}:2\)
\(=\frac{44}{245}\)
= 57/56
57/56 nha