Tính nhanh:
A= (1-1/2). (1-1/3). (1-1/4). (1-1/5). (1-1/6). (1-1/7). (1-1/8). (1-1/9)
Những câu hỏi liên quan
Tính nhanh:
a,1/3+3/4+2/3+1/4 b,3/4+3/5+2/8+4/10
c, 1/10+2/10+3/10+4/10+5/10+6/10+7/10+8/10+9/10
a)
`1/3+3/4+2/3+1/4`
`=1/3+2/3+3/4+1/4`
`=1+1`
`=2`
b)
`3/4+3/5+2/8+4/10`
`=3/4+2/8+3/5+4/10`
`=6/8+2/8+6/10+4/10`
`=1+1`
`=2`
c)
`1/10+2/10+3/10+4/10+5/10+6/10+7/10+8/10+9/10`
`=1/10+9/10+2/10+8/10+3/10+7/10+6/10+4/10+5/10`
`=1+1+1+1+5/10`
`=4+5/10`
`=40/10+5/10`
`=45/10=9/2`
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a: =1/3+2/3+3/4+1/4
=1+1
=2
b: =3/4+1/4+3/5+2/5
=1+1
=2
c: =(1+2+3+4+5+6+7+8+9)/10
=45/10
=9/2
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Tính nhanh:
a, \(\dfrac{8}{9}-\dfrac{1}{72}-\dfrac{1}{56}-\dfrac{1}{42}-\dfrac{1}{30}-\dfrac{1}{20}-\dfrac{1}{12}-\dfrac{1}{6}-\dfrac{1}{2}\)
b, \(\left(-\dfrac{1}{4}+\dfrac{7}{35}-\dfrac{5}{3}\right)-\left(-\dfrac{15}{12}+\dfrac{6}{11}-\dfrac{48}{49}\right)\)
a: Ta có: \(\dfrac{8}{9}-\left(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+...+\dfrac{1}{72}\right)\)
\(=\dfrac{8}{9}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{3}-...+\dfrac{1}{8}-\dfrac{1}{9}\right)\)
=0
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Tính nhanh:
a) ( 3/29 - 1/5) . 29/3
b) 3/4 . 7/9 + 1/4 . 7/9
c) 1/7 . 5/9 + 5/9 . 1/7 + 5/9 . 3/7
d) 4 . 11 . 3/4 . 9/121
a) \(\left(\dfrac{3}{29}-\dfrac{1}{5}\right)\cdot\dfrac{29}{3}\)
\(=\dfrac{3}{29}\cdot\dfrac{29}{3}-\dfrac{1}{5}\cdot\dfrac{29}{3}\)
\(=1-\dfrac{29}{15}\)
\(=\dfrac{15-29}{15}\)
\(=-\dfrac{14}{15}\)
b) \(\dfrac{3}{4}\cdot\dfrac{7}{9}+\dfrac{1}{4}\cdot\dfrac{7}{9}\)
\(=\dfrac{7}{9}\cdot\left(\dfrac{1}{4}+\dfrac{3}{4}\right)\)
\(=\dfrac{7}{9}\cdot1\)
\(=\dfrac{7}{9}\)
c) \(\dfrac{1}{7}\cdot\dfrac{5}{9}+\dfrac{5}{9}\cdot\dfrac{1}{7}+\dfrac{5}{9}\cdot\dfrac{3}{7}\)
\(=\dfrac{5}{9}\cdot\left(\dfrac{1}{7}+\dfrac{1}{7}+\dfrac{3}{7}\right)\)
\(=\dfrac{5}{9}\cdot\dfrac{5}{7}\)
\(=\dfrac{25}{63}\)
d) \(4\cdot11\cdot\dfrac{3}{4}\cdot\dfrac{9}{121}\)
\(=\left(4\cdot\dfrac{3}{4}\right)\cdot\left(11\cdot\dfrac{9}{121}\right)\)
\(=3\cdot\dfrac{9}{11}\)
\(=\dfrac{27}{11}\)
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Tính nhanh:a) 2.frac{3}{7}+left(frac{2}{9}-1frac{3}{7}right)-frac{5}{3}:frac{1}{9} b) frac{-11}{23}.frac{6}{7}+frac{8}{7}.frac{-11}{23}-frac{1}{23} c )left(frac{377}{-231}-frac{123}{89}+frac{34}{791}right).left(frac{1}{6}-frac{1}{8}-frac{1}{24}right) d) 19frac{5}{8}:frac{7}{12}-15frac{1}{4}:frac{7}{12} e) frac{2}{5}.frac{1}{3}-frac{2}{15}:frac{1}{5}+frac{3}{5}.frac{1}{3}
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Tính nhanh:
a) \(2.\frac{3}{7}+\left(\frac{2}{9}-1\frac{3}{7}\right)-\frac{5}{3}:\frac{1}{9}\)
b) \(\frac{-11}{23}.\frac{6}{7}+\frac{8}{7}.\frac{-11}{23}-\frac{1}{23}\)
c )\(\left(\frac{377}{-231}-\frac{123}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)
d) \(19\frac{5}{8}:\frac{7}{12}-15\frac{1}{4}:\frac{7}{12}\)
e) \(\frac{2}{5}.\frac{1}{3}-\frac{2}{15}:\frac{1}{5}+\frac{3}{5}.\frac{1}{3}\)
a: \(=\dfrac{17}{7}+\dfrac{2}{9}-\dfrac{10}{7}-\dfrac{5}{3}\cdot9=1+\dfrac{2}{9}-15=-14+\dfrac{2}{9}=-\dfrac{126}{9}+\dfrac{2}{9}=-\dfrac{124}{9}\)
b: \(=\dfrac{-11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)
c: \(=\left(\dfrac{377}{-231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot\dfrac{4-3-1}{24}=0\)
d: \(=\dfrac{12}{7}\left(19+\dfrac{5}{8}-15-\dfrac{1}{4}\right)=\dfrac{12}{7}\cdot\dfrac{35}{8}=\dfrac{15}{2}\)
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Tính nhanh bằng cách rút gọn rồi tính:
a.(1/2+1/3+1/4+1/5+1/6+1/7+1/8+1/9)-(1/3+1/4+1/5+1/6+1/7+1/8+1/9+1/10)
b.(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
Ai nhanh mình tick cho!
a) 1/2
b) 3/8
~~~~~~~~~hok tốt~~~~~~~~~~~~
A, 1/2; B, 3/8
A/ \(\frac{1}{2}\)
B/ \(\frac{3}{8}\)
Số ?2 1 + ... 6 2 + ... 8 ...+ 3 10 8 + ....3 1 + ... 6 ...+ 3 8 4 + .... 10 ...+ 34 ...+ 1 7 1 + ... 9 ...+ 1 10 6 + ...4 2 + ... 7 ...+ 2 9 ...+ 3 10 ...+ 55 ...+ 1 7 4 + .... 9 7 +.... 10 10 + ...5 3 +.... 8 ...+ 1 9 5 + ... 10 0 + .....6 ...+ 1 8 6 + ... 10 ...+ 1 1 1 + ....
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Số ?
2 = 1 + ... 6 = 2 + ... 8 = ...+ 3 10 = 8 + ....
3 = 1 + ... 6 =...+ 3 8 = 4 + .... 10 = ...+ 3
4 = ...+ 1 7 = 1 + ... 9 = ...+ 1 10 = 6 + ...
4 = 2 + ... 7 = ...+ 2 9 = ...+ 3 10 = ...+ 5
5 = ...+ 1 7 = 4 + .... 9 = 7 +.... 10 = 10 + ...
5 = 3 +.... 8 = ...+ 1 9 = 5 + ... 10 = 0 + .....
6 = ...+ 1 8 = 6 + ... 10 = ...+ 1 1 = 1 + ....
2 = 1 + 1 6 = 2 + 4 8 = 5 + 3 10 = 8 + 2
3 = 1 + 2 6 = 3 + 3 8 = 4 + 4 10 = 7 + 3
4 = 3 + 1 7 = 1 + 6 9 = 8 + 1 10 = 6 + 4
4 = 2 + 2 7 = 5 + 2 9 = 6+ 3 10 = 5 + 5
5 = 4 + 1 7 = 4 + 3 9 = 7 + 2 10 = 10 + 0
5 = 3 + 2 8 = 7 + 1 9 = 5 + 4 10 = 0 + 10
6 = 5 + 1 8 = 6 + 2 10 = 9 + 1 1 = 1 + 0
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Xem thêm câu trả lời
tính nhanh
(1+2+3+4+5+6+7+8+9).(1/2-1/3-1/4-1/5-1/6-1/7-1/8-1/9-1/0) /123
Tính:
5, 5 3/8 - 1 9/10
6, ( -3 1/4 ) + ( -2 1/3 )
7, ( -5 1/8 ) + 3 2/4
8, ( -6 1/7 ) + ( -7 1/6 )
5: \(=\dfrac{43}{8}-\dfrac{19}{10}=\dfrac{430}{80}-\dfrac{152}{80}=\dfrac{278}{80}=\dfrac{139}{40}\)
6: \(=\dfrac{-13}{4}-\dfrac{7}{3}=\dfrac{-39}{12}-\dfrac{28}{12}=\dfrac{-67}{12}\)
7: \(=\dfrac{-41}{8}+\dfrac{14}{4}=\dfrac{-41}{8}+\dfrac{28}{8}=\dfrac{-13}{8}\)
8: \(=\dfrac{-43}{7}+\dfrac{-43}{6}=\dfrac{-559}{42}\)
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