tính bằng cách thuận tiện nhất
9/11 + 6/15 + 2/11 + 9/ 15
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14/15 + 6/11 + 1/15 + 5/11 + 22/11
=(14/15 +1/15)+(6/11 + 5/11 + 22/11)
=1+3
=4
\(\frac{11}{15}\cdot\frac{6}{7}+\frac{11}{15}\cdot\frac{8}{7}\)
\(=\frac{11}{15}\cdot\left(\frac{6}{7}+\frac{8}{7}\right)\)
\(=\frac{11}{15}\cdot2=\frac{22}{15}\)
Chú ý dấu " \(\cdot\) " là dấu nhân
a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)
b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)
(2/7+5/7)+4/9=1+4/9=13/9
17/11+(7/15+5/11)=17/11+7/15+5/11=(17/11+5/11)+7/15=2+5/11=27/11
\(\dfrac{9}{4}\times\dfrac{15}{11}+\dfrac{3}{4}:\dfrac{11}{7}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times3\times\dfrac{15}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\dfrac{45}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\left(\dfrac{45}{11}+\dfrac{7}{11}-\dfrac{8}{11}\right)\)
\(=\dfrac{3}{4}\times4\)
\(=3\)
`9/4xx15/11+3/4:11/7-3/4xx8/11`
`=3/4xx15/11xx3+3/4xx7/11-3/4xx8/11`
`=3/4xx45/11+3/4xx7/11-3/4xx8/11`
`=3/4xx(45/11+7/11-8/11)`
`=3/4xx4`
`=3`
= 11/11+ 15/15
= 1+ 1
= 2
= 11/11+ 15/15
= 1+ 1
= 2
tick cho mk