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\(135.66-55.135-135-27.50\)
\(=135.66-135.55-135-1350\)
\(=135.66-135.55-135.1-135.10\)
\(=135.\left(66-55-1-10\right)\)
\(=135.0\)
\(=0\)
135 x 66 - 55 x 135 - 135 - 27 x 50
= 135 x (66 - 55 - 1 - 10)
= 135 x 0 = 0
Bài 1: Tính nhanh
d, 66 . 25 + 5 . 66 + 66 . 14 + 33 . 66
Bài 2: Tìm x
7 + ( 63 : X - 11 ) . 23 = 237
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1
\(d,66\cdot25+5\cdot66+66\cdot14+33\cdot66\)
\(=66\left(25+5+14+33\right)\)
\(=66\cdot77\)
\(=5082\)
Hình như chép sai đề vì không thể nào tính nhanh đc
Bài 2
\(7+\left(63:x-11\right)\cdot23=237\)
\(\Leftrightarrow\left(63:x-11\right)\cdot23=230\)
\(\Leftrightarrow63:X-11=10\)
\(\Leftrightarrow63:x=21\)
\(\Leftrightarrow x=3\)
Bài 1 :
\(d,66.25+5.66+66.14+33.66\)
\(=66.\left(25+5+14+33\right)\)
\(=66.77\)
\(=5082\)
Bài 2 :
\(7+\left(63:x-11\right).23=237\)
\(\Leftrightarrow\left(63:x-11\right).23=230\)
\(\Leftrightarrow63:x-11=10\)
\(\Leftrightarrow63:x=21\)
\(\Leftrightarrow x=3\)
Vậy x = 3 .
Học tốt nhé
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2/3 gio= 40 phut
Diện tích tam giác đáy :3.4m; cao :2.5 m
3.4*2.5/2=4.25 m2
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Bài 1:
\(A=\frac{1}{\left(1+2\right)}+\frac{1}{\left(1+2+3\right)}+\frac{1}{\left(1+2+3+4\right)}\)\(+\frac{1}{\left(1+2+3+4+5\right)}+...+\)\(\frac{1}{\left(1+2+3+...+10\right)}\)
\(A=\frac{1}{3}+\frac{1}{6}+....+\frac{1}{55}\)
\(A=2\left(\frac{1}{6}+\frac{1}{12}+....+\frac{1}{110}\right)\)
\(A=2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{10.11}\right)\)
\(A=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{10}-\frac{1}{11}\right)\)
\(A=2.\left(\frac{1}{2}-\frac{1}{11}\right)\)
\(A=\frac{9}{11}\)
Bài 2 :
2) Tử số = 11 x 13 x 15 + 3 x 3 x 3 x 11 x 13 x 15 + 5 x 5 x 5 x 11 x 13 x 15 + 9 x 9 x 9 x 11 x 13 x 15
= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) x 11 x 13 x 15 = (1+27+125+ 729) x 11 x 13 x 15
Mẫu số = 11 x 13 x 17 + 3 x 3 x 3 x 13 x 15 x 19 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17 lớn hơn 11 x 13 x 15 + 3 x 3 x 3 x 13 x 15 x 17 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17
= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) 13 x 15 x 17 = (1+27+125+729) x 13 x 15 x 17
\(\Rightarrow A< \frac{\left(1+27+125+729\right)\times11\times13\times15}{\left(1+27+125+729\right)\times13\times15\times17}\)
\(=\frac{11}{17}\)
\(=\frac{1111}{1717}=B\)
Vậy \(A=B\)
135/66 *2=135/33