tính bằng cách thuận tiện:
11/3 x 8/15 + 11/3 x 7/15
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Tính bằng cách thuận tiện nhất:
9/4 x 15/11 + 3/4 : 11/7 - 3/4 x 8/11
[Lưu ý trình bày cách làm ra!]
\(\dfrac{9}{4}\times\dfrac{15}{11}+\dfrac{3}{4}:\dfrac{11}{7}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times3\times\dfrac{15}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\dfrac{45}{11}+\dfrac{3}{4}\times\dfrac{7}{11}-\dfrac{3}{4}\times\dfrac{8}{11}\)
\(=\dfrac{3}{4}\times\left(\dfrac{45}{11}+\dfrac{7}{11}-\dfrac{8}{11}\right)\)
\(=\dfrac{3}{4}\times4\)
\(=3\)
`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`
tính bằng cách thuận tiện nhất
a,4/15 x 7/8 + 4/15 x 2/9
b, 13/29 x 23/11 -13/19 x 8/11 - 13/19 x 4/11
a.\(\dfrac{18}{15}+\dfrac{7}{15}+\dfrac{12}{15}=\dfrac{18+7+12}{15}=\dfrac{37}{15}\)
b.\(\dfrac{9}{7}+\dfrac{8}{7}+\dfrac{11}{7}=\dfrac{9+8+11}{7}=\dfrac{28}{7}=4\)
a, \(\dfrac{5\times11\times15\times18}{6\times15\times22\times10}\)
= \(\dfrac{5\times11\times15\times6\times3}{6\times15\times11\times2\times2\times5}\)
= \(\dfrac{5\times11\times15\times6}{5\times11\times15\times6}\) \(\times\) \(\dfrac{3}{2\times2}\)
= 1 \(\times\) \(\dfrac{3}{4}\)
= \(\dfrac{3}{4}\)
b, \(\dfrac{7}{12}\) \(\times\) \(\dfrac{3}{5}\) + \(\dfrac{3}{5}\) \(\times\) \(\dfrac{5}{12}\)
= \(\dfrac{3}{5}\) \(\times\) ( \(\dfrac{7}{12}+\dfrac{5}{12}\))
= \(\dfrac{3}{5}\) \(\times\) \(\dfrac{12}{12}\)
= \(\dfrac{3}{5}\) \(\times\) 1
= \(\dfrac{3}{5}\)
a) 18/15 + 7/15 + 12/15 =18/15 + 12/15 + 7/15
= 30/15 + 7/15
= 37/15
b) 9/7 + 8/7 +11/7 = 9/7 + 11/7 + 8/7
= 20/7 + 8/7 = 28/7 nha . tk mk nhé b
11/3 x 8/15 + 11/3 x 7/15
= 11/3 x (8/15 + 7/15)
= 11/3 x 1
= 11/3
123+123=642