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a. ( 29,38 - 3,25 x 5 + 36,36 : 3 ) : 6,25
= ( 29,38 - 16,25 + 12,12 ) : 6,25
= 25,25 : 6,25
= 4,04
b . ( 0,872 : 2,18 + 4,578 : 3,27 ) x 3,02 - 2,707
= ( 0,4 + 1,4 ) x 3,02 - 2,707
= 1,8 x 3,02 - 2,707
= 5,436 - 2,707
=2,729
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\(A=\frac{1\times111+2\times110+3\times109+...+111\times1}{1+\left(1+2\right)+\left(1+2+3\right)+...+\left(1+2+3+...+111\right)}\)
\(A=\frac{1\times111+2\times110+3\times109+...+111\times1}{\left(1+1+...+1\right)+\left(2+2+...+2\right)+...+111}\)(\(111\)số hạng \(1\), \(110\)số hạng \(2\),...)
\(A=\frac{1\times111+2\times110+3\times109+...+111\times1}{1\times111+2\times110+3\times109+...+111\times1}\)
\(A=1\)
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\(\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}\)
\(=\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}\right)\)
\(=\frac{1}{2}.\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}\right)\)
\(=\frac{1}{2}.\left(1-\frac{1}{9}\right)\)
\(=\frac{1}{2}.\frac{8}{9}\)
\(=\frac{4}{9}\)
#)Giải :
\(S=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+\frac{1}{7.9}\)
\(\Rightarrow2S=\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}\)
\(\Rightarrow2S=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}\)
\(\Rightarrow2S=1-\frac{1}{9}=\frac{8}{9}\)
\(S=\frac{8}{9}:2=\frac{4}{9}\)
#~Will~be~Pens~#
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Ta có 1/4 x 4/1 + 1/5 x 6/1 + 1/6 x 7/1 + 1/7 x 8/1
Ta có 1/4 x 4/1 = 1. => 1 + 6/5 + 7/6 + 8/7
1 + 6/5 + 7/6 + 8/7 = 11/5 + 7/6 + 8/7 = 101/30 + 8/7 = 947/210
P/S: MIK KO BIẾT CÁCH LÀM NHANH NÊN CHỈ THẾ NÀY THÔI !
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`6,25 : 0,25 + 6,25 xx 7 - 6,25`
`= 6,25 : 1/4 + 6,25 xx7-6,25 xx1`
`=6,25 xx 4 + 6,25xx7-6,25xx1`
`=6,25 xx (4+7-1)`
`=6,25 xx10`
`=62,5`.
![](https://rs.olm.vn/images/avt/0.png?1311)
mk bt làm mỗi 1 câu thui thông cảm
B) 37 x 62 + 37 x 38
37 x ( 62+38)
37 x 100
3700
hok tốt
a, 59 + 532 + 267 + 268 + 733
= 59 + ( 532 + 268 ) + ( 267 + 733 )
= 59 + 800 + 1000
= 859 + 1000
= 1859
b, 37 × 62 + 37 × 38
= 37 × ( 62 + 38 )
= 37 × 100
= 3 700
c, ( 1356 + 845 ) - ( 356 + 645 )
= 1356 + 845 - 356 - 645
= ( 1356 - 356 ) + ( 845 - 645 )
= 1000 + 200
= 1 200
( 29,38 - 3,25 x 5 + 36,36 : 3 ) : 6,25
= ( 29,38 - 16,25 + 12,12 ) : 6,25
= 25,25 : 6,25
= 4,04
= 4,04 k nha, năn nỉ đó.