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2000 : 25 = (2000 * 4) : (25 * 4) = 8000 : 100 = 80
7300 : 50 = (7300 * 2) : (50 * 2) = 14600 : 100 = 146
4970 : 50 = (4970 * 2) : ( 50 * 2) = 9940 : 100 = 99,4
81000 : 25 = (81000 * 4) : (25 * 4) = 324000 : 100 = 3240
2000: 25 = (2000 x 2 ) : ( 25 x 2 ) = 4000 : 50 = 80
7300 x 50 = ( 7300 x 2 ) : ( 50 x 2 ) =14600 : 100 = 146
4970 : 5 = ( 4970 x 2 ) : ( 5 x2 ) = 9940 : 10 = 994
81000 : 25 = ( 81000 x 2 ) : ( 25 x 2 ) = 162000 : 50 = 3240
![](https://rs.olm.vn/images/avt/0.png?1311)
66\(\times\)50=3300
72\(\times\)125=9000
38\(\times\)5=190
2000\(\div\)=80
7300\(\div\)50=146
4970\(\div\)5=994
81000\(\div\)648
Học tốt!
Tính nhẩm
a) 66.50 = 3300
b) 72.125 = 9000
c) 38.5 = 190
d) 2000:25 = 80
e) 7300:50 = 146
g) 4970:5 = 994
h) 81000:125 = 648
![](https://rs.olm.vn/images/avt/0.png?1311)
499.12 = 5988
7300 : 50 = 146
204 : 12 = 17
601.42 = 25242
4970 : 5 = 994
199.41 = 8159
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\text{a) -3000 : 2 + 5(2x-1) = 125}\\ -1500+5\left(2x-1\right)=125\\ 5\left(2x-1\right)=125-\left(-1500\right)\\ 5\left(2x-1\right)=1625\\ 2x-1=1625:5\\ 2x-1=325\\ 2x=325+1\\ 2x=326\\ x=326:2\\ x=163\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a)b) đợi tí hơi dài đấy
c) 2000 : 25
= 20 . 100 : 25
= 20 . 4
= 80
d) 7300 : 50
= 73 . 100 : 50
= 73 . 2
= 146
Tính nhanh :
a) 1 + 3 + 5 + ... + ( 2n - 1 )
= [ ( 2n - 1 ) - 1 ] : 2
= n
b) 2 + 4 + 6 + 8 + ... + 2n
= ( 2n-2) : 2
= n-1
c) 2000 : 25
= 80
d) 7300 : 50
= 146
![](https://rs.olm.vn/images/avt/0.png?1311)
b) Ta có: \(x-43=\left(57-x\right)-50\)
\(\Leftrightarrow x-43=57-x-50\)
\(\Leftrightarrow x+x=7+43\)
\(\Leftrightarrow2x=50\)
hay x=25
Vậy: x=25
c) Ta có: (x-2)(8-x)=0
\(\Leftrightarrow\left[{}\begin{matrix}x-2=0\\8-x=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=8\end{matrix}\right.\)
Vậy: \(x\in\left\{2;8\right\}\)
a) 400
b) 146
c) 994
d)648
e)24
f)98
\(a.2000:5=40\)
\(b.7300:50=146\)
\(c.4970:5=994\)
\(d.81000:125=648\)
\(e.3000:125=24\)
\(f.490:5=98\)