tính bằng cách thuận tiện nhất
17/2 nhan3/5 + 3/5 nhân 1/2 + 3/5
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= 17/2 x 3/5 + 3/5 x 1/2 + 3/5 x 1
= 3/5 x ( 17/2 + 1/2 + 1 )
= 3/5 x 10
= 30/5
= 1/6
\(\frac{17}{2}\cdot\frac{3}{5}+\frac{3}{5}\cdot\frac{1}{2}+\frac{3}{5}\)
\(=\left(\frac{17}{2}+\frac{1}{2}+1\right)\cdot\frac{3}{5}\)
\(=\left(\frac{17}{2}+\frac{1}{2}+\frac{2}{2}\right)\cdot\frac{3}{5}\)
\(=10\cdot\frac{3}{5}=6\)
\(\frac{17}{2}\times\frac{3}{5}+\frac{3}{5}\times\frac{3}{2}\)
\(=\left(\frac{17}{2}+\frac{3}{2}\right)\times\frac{3}{5}\)
\(=\frac{20}{2}\times\frac{3}{5}\)
\(=10\times\frac{3}{5}\)
\(=\frac{30}{5}=6\)
\(\frac{5}{5}x\)\(\frac{17}{21}+\frac{17}{21}x\)\(\frac{2}{5}\)
=(\(\frac{5}{5}+\frac{2}{5}\)) x\(\frac{17}{21}\)
=\(\frac{7}{5}x\)\(\frac{17}{21}\)
\(\frac{119}{105}\)
`a) 5 / 13 xx 4 / 15 xx 13 = [ 5 xx 4 xx 13 ] / [ 13 xx 5 xx 3 ] = 4 / 3`
`b) ( 3 / 7 + 5 / 2 ) xx 7 / 5 = 3 / 7 xx 7 / 5 + 5 / 2 xx 7 / 5 = 3 / 5 + 7 / 2 = 6 / 10 + 35 / 10 = 41 / 10`
`c) 1 / 5 xx 11 / 18 + 11 / 18 xx 3 / 5 = 11 / 18 xx ( 1 / 5 + 3 / 5 ) = 11 / 18 xx 4 / 5 = [ 11 xx 2 xx 2 ] / [ 2 xx 9 xx 5 ] = 22 / 45`
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{4}{3}\)
\(b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\left(\dfrac{6}{14}+\dfrac{35}{14}\right)\times\dfrac{7}{5}=\dfrac{41}{14}\times\dfrac{7}{15}=\dfrac{41}{30}\)
\(c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
5,5 + \(\dfrac{3}{4}\) - 5 + \(\dfrac{1}{4}\)
(5,5 - 5) + (\(\dfrac{3}{4}\) + \(\dfrac{1}{4}\))
= 0,5 + 1
= 1,5
\(\dfrac{5}{2}\) x \(\dfrac{2}{3}\) + \(\dfrac{1}{4}\) : \(\dfrac{3}{2}\)
= \(\dfrac{5}{2}\) x \(\dfrac{2}{3}\) + \(\dfrac{1}{4}\) x \(\dfrac{2}{3}\)
= (\(\dfrac{5}{2}\) + \(\dfrac{1}{4}\)) x \(\dfrac{2}{3}\)
= (\(\dfrac{10}{4}\) + \(\dfrac{1}{4}\)) x \(\dfrac{2}{3}\)
= \(\dfrac{11}{4}\) x \(\dfrac{2}{3}\)
= \(\dfrac{11}{6}\)
Tính \(x\):
435 - [\(x\) + 16] = 425 : 17
435 - [\(x\) + 16] = 25
[\(x\) + 16] = 435 - 25
\(x\) + 16 = 410
\(x\) = 410 - 16
\(x\) = 394
\(\frac{1}{7}x\frac{3}{5}+\frac{3}{5}x\frac{1}{2}+\frac{3}{5}\)
\(=\frac{3}{5}.\left(\frac{1}{7}+\frac{1}{2}+1\right)\)
\(=\frac{3}{5}x\left(\frac{2}{14}+\frac{7}{14}+\frac{14}{14}\right)\)
\(=\frac{3}{5}x\frac{23}{14}\)
\(=\frac{69}{70}\)
Tham khảo nha !!!