Thực hiện phép tính một cách hợp lí:
a) 1/7. (-3/8)+1/7. (-13/8)
b) 3/5.13/46-1/10.16/23
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TU
1
YN
19 tháng 9 2021
\(\frac{3}{7}.\frac{9}{26}-\frac{1}{14}.\frac{1}{13}\)
\(=\frac{27}{182}-\frac{1}{182}\)
\(=\frac{1}{7}\)
\(\frac{3}{5}.\frac{13}{46}-\frac{1}{10}.\frac{16}{23}\)
\(=\frac{6}{10}.\frac{13}{46}-\frac{1}{10}.\frac{16}{23}\)
\(=\frac{1}{10}.\frac{78}{46}-\frac{1}{10}.\frac{16}{32}\)
\(=\frac{1}{10}\left(\frac{78}{46}-\frac{32}{46}\right)\)
\(=\frac{1}{10}.1=\frac{1}{10}\)
1 tháng 8 2021
\(\text{Phần a nên sửa đề thế này :}\) \(\frac{1}{7}.\frac{-3}{8}+\frac{1}{7}.\frac{-13}{8}\)
\(\text{Giải :}\)
\(\frac{1}{7}.\frac{-3}{8}+\frac{1}{7}.\frac{-13}{8}\)
\(=\frac{1}{7}\left(\frac{-3}{8}+\frac{-13}{8}\right)\)
\(=\frac{1}{7}.\left(-2\right)\)
\(=\frac{-2}{7}\)
1 tháng 8 2021
\(\frac{3}{5}.\frac{13}{46}-\frac{1}{10}.\frac{16}{23}\)
\(=\frac{3}{5}.\left(\frac{1}{46}.13\right)-\frac{1}{10}.\frac{32}{46}\)
\(=\left(\frac{3}{5}.13\right).\frac{1}{46}-\left(\frac{1}{10}.32\right).\frac{1}{46}\)
\(=\frac{39}{5}.\frac{1}{46}-\frac{32}{10}.\frac{1}{46}\)
\(=\frac{78}{10}.\frac{1}{46}-\frac{32}{10}.\frac{1}{46}\)
\(=\left(\frac{78}{10}-\frac{32}{10}\right).\frac{1}{46}\)
\(=\frac{46}{10}.\frac{1}{46}\)
\(=\frac{1}{10}\)
KQ
28 tháng 2 2023
`a)3/5+(-4/9)`
`=3/5-4/9`
`=27/45-20/45`
`=7/45`
`b)3/5+2/5 . 15/8`
`=3/5 + 30/40`
`=3/5+3/4`
`=12/20+15/20`
`=27/20`
`c)7/2 . 8/13 + 8/13 . (-5/2)`
`=8/13 . (7/2 +(-5)/2)`
`=8/13 . 1`
`=8/13`
`d)-5/17 . (-9/23)+9/23 . (-22/17) + 11 9/23`
`=-5/17 . (-9/23) + 9/23 . (-1) . 22/17 + 11 + 9/23`
`=-5/17 . (-9/23) + (-9/23) . 22/17+11+9/23`
`= -9/23 ( -5/17 + 22/17)+11+9/23`
`= - 9/23 . 1+11+9/23`
`=-9/23+11+9/23`
`=(-9/23+9/23)+11`
`=0+11`
`=11`
28 tháng 2 2023
a: =27/45-20/45=7/45
b: =3/5+30/40
=3/5+3/4
=12/20+15/20
=27/20
c: =8/13(7/2-5/2+1)=8/13*2=16/13
d: =9/23*5/17-9/23*22/17+11+9/23
=-9/23+11+9/23
=11
28 tháng 6 2016
a) \(\frac{3}{5}\cdot\frac{13}{46}-\frac{1}{10}\cdot\frac{16}{23}=\frac{39-16}{10\cdot23}=\frac{1}{10}\)
b) \(\frac{3}{7}\cdot\frac{9}{26}-\frac{1}{14}\cdot\frac{1}{13}=\frac{27-1}{14\cdot13}=\frac{2\cdot13}{2\cdot7\cdot13}=\frac{1}{7}\)
T
28 tháng 8 2018
\(a.\frac{1}{7}\times\frac{-3}{8}+\frac{-13}{8}==\frac{-3}{56}+\frac{-13}{8}=\frac{-3}{56}+\frac{-91}{56}=\frac{-94}{56}=\frac{-47}{28}\)
\(b.\frac{3}{5}\times\frac{13}{40}-\frac{1}{10}\times\frac{16}{23}=\frac{39}{200}-\frac{8}{115}=\frac{577}{4600}\)
\(c.\left(\frac{-3}{4}+\frac{2}{5}\right):\frac{3}{7}+\left(\frac{3}{5}+\frac{1}{4}\right):\frac{3}{7}\)
\(=\left(\frac{-3}{4}+\frac{2}{5}\right)\times\frac{7}{3}+\left(\frac{3}{5}+\frac{1}{4}\right)\times\frac{7}{3}\)
\(=\frac{7}{3}\times\left(\frac{-3}{4}+\frac{2}{5}+\frac{3}{5}+\frac{1}{4}\right)\)
\(=\frac{7}{3}\times\left[\left(\frac{-3}{4}+\frac{1}{4}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)\right]\)
\(=\frac{7}{3}\times\left(\frac{-2}{4}+1\right)\)
\(=\frac{7}{3}\times\frac{1}{2}\)
\(=\frac{7}{6}\)
\(d.\frac{7}{8}:\left(\frac{2}{9}-\frac{1}{8}\right)+\frac{7}{8}:\left(\frac{1}{6}-\frac{5}{12}\right)\)
\(=\frac{7}{8}:\frac{7}{72}+\frac{7}{8}:\left(\frac{-1}{4}\right)\)
\(=\frac{7}{8}\times\frac{72}{7}+\frac{7}{8}\times-4\)
\(=\frac{7}{8}\times\left(\frac{72}{7}+\left(-4\right)\right)\)
\(=\frac{7}{8}\times\frac{44}{7}\)
\(=\frac{11}{2}\)
PN
1
1 tháng 8 2021
\(\frac{3}{5}.\frac{13}{46}-\frac{1}{10}.\frac{16}{23}\)
\(=\frac{3}{5}.\left(\frac{1}{46}.13\right)-\frac{1}{10}.\frac{32}{46}\)
\(=\left(\frac{3}{5}.13\right).\frac{1}{46}-\left(\frac{1}{10}.32\right).\frac{1}{46}\)
\(=\frac{39}{5}.\frac{1}{46}-\frac{32}{10}.\frac{1}{46}\)
\(=\frac{78}{10}.\frac{1}{46}-\frac{32}{10}.\frac{1}{46}\)
\(=\left(\frac{78}{10}-\frac{32}{10}\right).\frac{1}{46}\)
\(=\frac{46}{10}.\frac{1}{46}\)
\(=\frac{1}{10}\)
NL
4
PV
16 tháng 3 2017
13 - 12 + 11 + 10 - 9 + 8 - 7 - 6 + 5 - 4 + 3 + 2 - 1
= 1 + 11 - 1 + 1 + 11 - 7 + 1
= 12 - 1 + 1 + 11 - 7 + 1
= 11 + 1 + 11 - 7 + 1
= 12 + 11 - 7 + 1
= 23 - 7 + 1
= 16 + 1
=17
a) \(\dfrac{1}{7}.\dfrac{-3}{8}+\dfrac{1}{7}.\dfrac{-13}{8}\)
\(=\dfrac{1}{7}.\left(\dfrac{-3}{8}+\dfrac{-13}{8}\right)\)
\(=\dfrac{1}{7}.\left(-2\right)\)
\(=\dfrac{-2}{7}\)
b) \(\dfrac{3}{5}.\dfrac{13}{46}-\dfrac{1}{10}.\dfrac{16}{23}\)
\(=\dfrac{39}{230}\) - \(\dfrac{8}{115}\)
\(=\dfrac{1}{10}\)
a, \(\dfrac{1}{7}.\left(-\dfrac{3}{8}\right)+\dfrac{1}{7}.\left(-\dfrac{13}{8}\right)\)
=> \(\dfrac{1}{7}.\left[\left(-\dfrac{3}{8}\right)+\left(-\dfrac{13}{8}\right)\right]\)
=> \(\dfrac{1}{7}.-\dfrac{16}{8}\)
=> \(\dfrac{1}{7}.\left(-2\right)\)
=> \(\dfrac{-2}{7}\)