Tính bằng cách thuận tiện: 14/19 - 5/7 + 5/19 + 47/7 = ?
lm hẳn lười giải ra cho mik.
Cảm ơn mn!
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a, \(\frac{2}{5}\)x ( \(\frac{3}{7}\)+\(\frac{4}{7}\))
= \(\frac{2}{5}\)x \(\frac{7}{7}\)
= \(\frac{2}{5}\)x 1
= \(\frac{2}{5}\)
b, \(\frac{47}{19}\) :\(\frac{15}{32}\) - \(\frac{47}{19}\) :\(\frac{15}{17}\)
= \(\frac{47}{19}\) × \(\frac{32}{15}\) - \(\frac{47}{19}\) × \(\frac{17}{15}\)
= \(\frac{47}{19}\) × (\(\frac{32}{15}\)-\(\frac{17}{15}\))
= \(\frac{47}{19}\) × 1
= \(\frac{47}{19}\)
`( 9 xx 6 xx 5 xx 7 )/( 19 xx 7 xx 2 xx 3 )`
`= ( 9 xx 2 xx 3 xx 7 xx 5 )/( 19 xx 7 xx 2 xx 3 )`
`= (9xx5)/19`
`= 45/19`
A =\(\frac{2}{5}\times\frac{4}{7}+\frac{3}{5}\times\frac{4}{7}\) B = \(\frac{17}{13}\times\frac{12}{17}-\frac{4}{13}\times\frac{12}{17}\) C = \(\frac{9}{14}:\frac{6}{7}+\frac{5}{14}:\frac{6}{7}\) D =\(\frac{9}{12}:\frac{7}{9}\times\frac{12}{19}\)
= \(\frac{4}{7}\times\left(\frac{2}{5}+\frac{3}{5}\right)\) =\(\left(\frac{17}{13}-\frac{4}{13}\right)\times\frac{12}{17}\) = \((\frac{9}{14}+\frac{5}{14}):\frac{6}{7}\) = \(\frac{9}{12}\times\frac{9}{7}\times\frac{12}{19}\)
=\(\frac{4}{7}\times1\) = \(1\times\frac{12}{17}\) = \(1:\frac{6}{7}\) = \(\frac{9\times9\times12}{12\times7\times19}\)
=\(\frac{4}{7}\) = \(\frac{12}{17}\) =\(\frac{7}{6}\) = \(\frac{9\times9}{7\times19}=\frac{81}{133}\)
\(\dfrac{3}{5}+\dfrac{6}{11}+\dfrac{7}{13}+\dfrac{2}{5}+\dfrac{16}{11}+\dfrac{19}{13}\\ =\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{6}{11}+\dfrac{16}{11}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)\\ =\dfrac{5}{5}+\dfrac{22}{11}+\dfrac{26}{13}\\ =1+2+2\\ =5\)
$#Shả$
`A)=5/17xx(15/34+19/34)`
`=5/17xx1=5/17`
`B)=(13/12+7/12)+1/3`
`=5/3+1/3=2`
a) \(19\times\left(52+38\right)-9\times\left(52+38\right)=\)
\(=\) \(19\times90-9\times90\)
\(=90\times\left(19-9\right)\)
\(=90\times10\)
\(=900\)
b) \(\dfrac{2}{5}\div\dfrac{3}{7}\times\dfrac{3}{7}\div\dfrac{2}{5}+2019=\)
\(=\left(\dfrac{2}{5}\div\dfrac{2}{5}\right)\times\left(\dfrac{3}{7}\div\dfrac{3}{7}\right)+2019\)
\(=1\times1+2019\)
\(=2019\)
`4/6+7/13+17/9+19/13+1/9+14/6`
`=(4/6+14/6)+(7/13+19/13)+(17/9+1/9)`
`=18/6+26/13+18/9`
`=3+2+2`
`=7`
(19+1)+(18+2)+(17+3)+(16+4)+(15+5)+(14+6)+(13+7)+(12+8)+(11+9)+20)+10
=20+20+20+20+20+20+20+20+20+20=(20*10)+10
=210
1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20
=(1+19)+(2+18)+(3+17)+(4+16)+(5+15)+(6+14)+(7+13)+(8+12)+(9+11)+(10+20)
=20+20+20+20+20+20+20+20+20+30
=(20 x 9) + 30
=180 + 30
=210
tk nha
\(\dfrac{14}{19}+\dfrac{5}{19}-\dfrac{5}{7}+\dfrac{47}{7}=\dfrac{19}{19}+\dfrac{42}{7}=1+6=7\)
19/19 + 42/7 = 1 + 6 =7