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câu b không làm được tính chất phân phối giũa phép nhân với phép cộng
![](https://rs.olm.vn/images/avt/0.png?1311)
(Dấu . là dấu nhân)
a/\(\dfrac{2}{5}\cdot\dfrac{4}{3}-\dfrac{2}{5}:3\)
\(=\dfrac{2}{5}\cdot\dfrac{4}{3}-\dfrac{2}{5}\cdot\dfrac{1}{3}\)
\(=\dfrac{2}{5}\cdot\left(\dfrac{4}{3}-\dfrac{1}{3}\right)\)
\(=\dfrac{2}{5}\cdot1\)
\(=\dfrac{2}{5}\)
b/\(\dfrac{2010}{2018}:\dfrac{1}{2}+\dfrac{7}{2018}:\dfrac{1}{2}\)
\(=\left(\dfrac{2010}{2018}+\dfrac{7}{2018}\right):\dfrac{1}{2}\)
\(=\dfrac{2017}{2018}:\dfrac{1}{2}\)
\(=\dfrac{2017}{2018}\cdot2\)
\(=\dfrac{2017}{1009}\)
a, \(\dfrac{2}{5}\) \(\times\) \(\dfrac{4}{3}\) - \(\dfrac{2}{5}\) : 3
= \(\dfrac{2}{5}\) \(\times\) \(\dfrac{4}{3}\) - \(\dfrac{2}{5}\) \(\times\) \(\dfrac{1}{3}\)
= \(\dfrac{2}{5}\) \(\times\) ( \(\dfrac{4}{3}\) - \(\dfrac{1}{3}\))
= \(\dfrac{2}{5}\) \(\times\) 1
= \(\dfrac{2}{5}\)
b, \(\dfrac{2010}{2018}\) : \(\dfrac{1}{2}\) + \(\dfrac{7}{2018}\) : \(\dfrac{1}{2}\) + \(\dfrac{1}{2018}\) : \(\dfrac{1}{2}\)
= \(\dfrac{2010}{2018}\) \(\times\) \(\dfrac{2}{1}\) + \(\dfrac{7}{2018}\) \(\times\) \(\dfrac{2}{1}\) + \(\dfrac{1}{2018}\) \(\times\) \(\dfrac{2}{1}\)
= \(\dfrac{2}{1}\) \(\times\) ( \(\dfrac{2010}{2018}\) + \(\dfrac{7}{2018}\) + \(\dfrac{1}{2018}\))
= 2 \(\times\) \(\dfrac{2018}{2018}\)
= 2 \(\times\) 1
= 2
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Tính bằng cách thuận tiện nhất:
2018 : 1/2 + 2018 :1/3 + 2018 : 1/4 +2018
= 2018 : 1/2 + 2018 :1/3 + 2018 : 1/4 +2018 : 1
= 2018 : (1/2 + 1/3 + 1/4 + 1 )
= 2018 : 25/12
= 968,64.
Mk ko bít đúng không nhưng mình cứ đăng lên, nếu sai thì thông cảm nhé.
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6346-654+3654-2346
=(6346-2346)+(3654-654)
=4000+3000
=7000
P/s tham khảo nha
ta có: 6346 - 654 + 3654 - 2346
= ( 6346 - 2346)+ ( -654 +3654)
= 4000 + 3000
=7000
RẤT VUI ĐC GIÚP BẠN :)
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\(2018\times2+98\times2018=2018\times\left(2+98\right)=2018\times100=201800\) theo mình nghĩ cách tính gộp này nhanh nhất
cách 1 : (đặt thừa số chung)
2018 x 2 + 98 x 2018
= 2018 x ( 98 + 2)
= 2018 x 100
= 201 800
Cách 2 : thực hiện theo thứ tự thực hiện phép tính :
2018 x 2 + 98 x 2018
= 4036 + 197764
= 201 800
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{1}{10}+\dfrac{4}{20}+\dfrac{9}{30}+\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
\(=\dfrac{1}{10}+\dfrac{1}{5}+\dfrac{3}{10}+\dfrac{2}{5}+\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{10}+\dfrac{4}{5}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{3}{10}+\dfrac{7}{10}+\dfrac{9}{10}\right)+\left(\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}\right)+\dfrac{1}{2}\)
\(=2+2+\dfrac{1}{2}\)
\(=4+\dfrac{1}{2}\)
\(=\dfrac{8}{2}+\dfrac{1}{2}=\dfrac{9}{2}\)
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a) 62389 + 4402 - 20389
= (62389 - 20389) + 4402
= 42000 + 4402
= 46402
b) 83268 + 15739 + 16732
=(83268 + 16732) + 15739
= 100 000 + 15 739
= 115 739
c) 30 + 35 + 40 + 45 + 50 + 55 + 60 + 65 + 70
=(30 + 70) + (35 + 65) + (40 + 60) + (45 + 55) + 50
= 100 + 100 + 100 + 100 + 50
= 100 x 4 + 50
= 400 + 50 = 450
a) 2018 x 30 + 2018 x 70 = ?
Cách 1: 2018 x 30 + 2018 x 70 = 60540 + 141260
= 201800
Cách 2: 2018 x 30 + 2018 x 70 = 2018 x (30 + 70)
= 2018 x 100
= 201800
b) 654 x 60 + 654 x 40 = ?
Cách 1: 654 x 60 + 654 x 40 = 39240 + 26160
= 65400
Cách 2: 654 x 60 + 654 x 40 = 654 x (60 + 40)
= 654 x 100
= 65400