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\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)
\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)
\(=\frac{5}{15}+\frac{12}{18}\)
\(=\frac{1}{3}+\frac{2}{3}\)
\(=\frac{3}{3}=1\)
\(\frac{1}{15}+\frac{4}{15}+\frac{5}{18}+\frac{7}{18}\)
\(=\left(\frac{1}{15}+\frac{4}{15}\right)+\left(\frac{5}{18}+\frac{7}{18}\right)\)
\(=\frac{1}{3}+\frac{2}{3}\)
\(=1\)
mỗi một dòng cuối câu vẫn phải viết thêm `
vd:
`3xx4/15-2xx4/15-5xx4/15`
`=4/15xx(3-2-5)`
`=4/15xx-4`
`=-16/15`
a) \(60\times\left(\frac{7}{12}+\frac{4}{15}\right)=\frac{60\times7}{12}+\frac{60\times4}{15}\)
\(=\frac{12\times5\times7}{12}+\frac{15\times4\times4}{15}\)
\(=5\times7+4\times4\)
\(=35+16\)
\(=51\)
\(\frac{19}{15}+\frac{31}{23}-\frac{4}{15}-\frac{8}{23}=\frac{19-4}{15}+\frac{31-8}{23}=\frac{15}{15}+\frac{23}{23}=1+1=2\)
\(\frac{19}{15}+\frac{31}{23}-\frac{4}{15}-\frac{8}{23}\)
\(=\frac{19-4}{15}+\frac{31-8}{23}\)
\(=\frac{15}{15}+\frac{23}{23}\)
\(=1+1=2\)
=15/17 x (4/7 + 3/7) - 1/3
=15/17 x 1 - 1/3
=15/17 x (3/3 - 1/3)
=15/17 x 2/3
=30/51
2 x 4 x 5 x 6 x 15 x 25
= (2x5)x(6x15)x(4x25)
= 10 x 90 x 100
= 90000
2x4x5x6x15x25
=[2x5]x[4x25]x[6x15]
=10x100x90
=1000x90
=90000
h cho minh do ha
\(\dfrac{15}{8}\) : \(\dfrac{5}{20}\) - \(\dfrac{7}{8}\) : \(\dfrac{1}{4}\)
= \(\dfrac{15}{8}\) : \(\dfrac{1}{4}\) - \(\dfrac{7}{8}\) : \(\dfrac{1}{4}\)
= ( \(\dfrac{15}{8}\) - \(\dfrac{7}{8}\)) : \(\dfrac{1}{4}\)
= \(\dfrac{8}{8}\) \(\times\) 4
= 4