Bài 1. Thực hiện các phép tính sau bằng cách hợp lí nhất:
b) 25.4+4.91.25 +25
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{45.21.25}{7.15.36}=\dfrac{3.3.3.5.7.5.5}{7.5.3.3.2.3.2}=\dfrac{25}{4}\)
45\7 x 21\15 x 25/36
=45x21x25/7x15x36
=15x3x7x3x25/7x15x3x12
=3x25/12
=75/12
=25/4
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,25.\left(7-27\right)+27.25\)
\(=25.7-27+27.25\)
\(=27.\left(25+25\right)-7\)
\(=27.50-7=135-7=128\)( ko chắc )
\(b,\left(-3\right)^2.\left(-2\right)^3\)
\(=9.\left(-8\right)=-72\)
![](https://rs.olm.vn/images/avt/0.png?1311)
B) 42.53+47.156-47.114
=42.53+47(156-114)
=42.53+47.42
=42(53+47)
=42.100
=4200
341.67+341.6+659.83
=341.(67+6)+659.83
=341.83+659.83
=(341+659).83
=1000.83
=83000.
42.53+47.156-47.114
=42.53+47.(156-114)
=42.53+47.42
=42.(53+47)
=42.100.
NẾU ĐÚNG THÌ K OK OK OK OK
=4200
![](https://rs.olm.vn/images/avt/0.png?1311)
a. 4.52.5.25.2
=(4.25).(5.2).52
=100.10.52
=1000.52
=52000
b. 2.32 + 4.32
=32 . (2+4)
=9.6
=54
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,38+41+117+159+62\\ =\left(38+62\right)+\left(41+159\right)+117\\ =100+200+117\\ =300+117\\ =417.\\ b,73+86+914+3032\\ =73+1000+3032\\ =1073+3032\\ =5150.\\ c,314.67+314.16+659.83\\ =314.\left(67+16\right)+659.83\\ =314.83+659.83\\ =83.\left(314+659\right)\\ =83.937\\ =?\)
Bn xem lại phần \(c,\) .
\(d,42.53+47.156-47.114\\ =42.53+47.\left(156-114\right)\\ =42.53+47.42\\ =42.\left(53+47\right)\\ =42.100\\ =4200.\)
a) \(38+41+117+159+62=(38+62)+(41+159)+117 \)
\(=100+200+117 =300+117 =417\)
b) \(73+86+968+914+3032=(86+914)+(968+3032)+73\)
\(=1000+4000+73=5073\)
c) \(341.67+341.16+659.83 =341.(67+16)+659.83 =341.83+659.83\)
\(=83.(341+659) =83.1000=83000\)
d) \(42.53+47.156-47.114 =42.53+47(156-114) =42.53+47.42 =42.(53+47)=42.100=4200\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\frac{9}{25}-2.18\right):\left(3\frac{4}{5}-0,2\right)\)
= -1,82:4=-0,455
![](https://rs.olm.vn/images/avt/0.png?1311)
a,-20 - (25 -11 +8) + (25 + 8 +20)
= -20 - 25 + 11 - 8 + 25 + 8 + 20
= 11
b,79.89 - 79.(-11) - 100.79
= 79( 89 + 11 -100)
= 79 ( 100 - 100)
= 79 . 0
= 0
hok tốt!!
Em gõ phép tính ra nha em
25.4 + 4.91.25 + 25
= 25.4(1+91) + 25
=100.91 + 25
=9100 + 25
=9125