tính thuận tiện 23 23 x2 23 x 3 23 x 4
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TL:
a)25 x 12 x 30 x 4
= (25 x 5) x (12 x 30)
= 100 x 360
= 36000
b)23 + 23 x 2 + 23 x 3 +23 x 4
= 23 x 1 + 23 x 2 + 23 x 3 +23 x 4
= 23 x (1 + 2 + 3 + 4)
= 23 x 10
= 230
c)248 x 2005 - 2005 x 148
= (248 - 148) x 2005
= 100 x 2005
= 200500
HT
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TL:
8/15 x 5/6 = 40/90 = 4/9
41/20 x 3/4 = 123/80
(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43
HT
\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)
\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)
\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)
/HT\
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 25 x 12 x 30 x 4
=(25 x 4 ) x (12 x 30 )
=100 x 360
=3600
b) 23 + 23 x 2 + 23 x 3 + 23 x 4
=23 x 1 +23 x 2 +23 x 3+23 x4
=23 x (1+2+3+4)
=23 x 10=230
c)248 x 2005 - 2005 x 148
=2005 x (248-148)
=2005 x 100
=200500
Hok tốt k nha
![](https://rs.olm.vn/images/avt/0.png?1311)
( 20,33 + 35,12) x 33 – 45,45 x 23 – 10 x 23
= 55,45 x 33 - (45,45 + 10) x 23
= 55,45 x 33 - 55,45 x 77
= 55,45 x ( 33 - 23)
= 55, 45 x 10 = 554,5
![](https://rs.olm.vn/images/avt/0.png?1311)
( 20,33 + 35,12) x 33 – 45,45 x 23 – 10 x 23
= 55,45 x 33-(45,45 + 10) x 23
= 55,45x 33-55,45 x 77
= 55,45 x ( 33 - 23)
= 55, 45 x 10
= 554,5
![](https://rs.olm.vn/images/avt/0.png?1311)
A. 64 : 16 = 4
B. 210 : 30 = 7
C. 504 : 56 = 9
D. 115 : 23 = 5