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\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)
\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)
\(=60\times\frac{51}{60}\)
\(=51\)
\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))
= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)
= 35 + 16
= 51
\(\left(\dfrac{2}{7}+\dfrac{5}{7}\right)+\left(\dfrac{3}{5}+\dfrac{2}{5}\right)+\left(\dfrac{3}{8}+\dfrac{4}{8}+\dfrac{1}{8}\right)+\left(\dfrac{1}{9}+\dfrac{8}{9}\right)=1+1+1+1=4\)
7/8 x 1/4 + 7/8 x 2/4 + 7/8
=7/8 x\(\left(\dfrac{1}{4}+\dfrac{2}{4}\right)\) + 7/8
=7/8 x 3/4 + 7/8
=7/8 x \(\left(\dfrac{3}{4}+1\right)\)
=7/8 x 7/4
=49/32
`7/8 xx 1/4 + 7/8 xx 2/4 + 7/8`
`= 7/8 xx 1/4 + 7/8 xx 2/4 + 7/8xx1`
`= 7/8 xx (1/4 +2/4+1)`
`= 7/8 xx ( 3/4 + 4/4)`
`= 7/8 xx 7/4`
`= 49/32`
` @ nkhanh`