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\(\frac{8}{9}\):\(\frac{3}{4}\).\(\frac{5}{8}\)
=\(\frac{8}{9}\).\(\frac{4}{3}\).\(\frac{5}{8}\)
=\(\frac{8.4.5}{9.3.8}\)
=\(\frac{160}{216}\)
=0,(740)
\(\left(\dfrac{3}{2}\times\dfrac{5}{7}+\dfrac{3}{2}\times\dfrac{7}{2}-\dfrac{3}{2}+\dfrac{3}{2}\right):\dfrac{3}{2}\)
\(=\left[\dfrac{3}{2}\times\left(\dfrac{5}{7}+\dfrac{7}{2}\right)-\left(\dfrac{3}{2}-\dfrac{3}{2}\right)\right]:\dfrac{3}{2}\)
\(=\left[\dfrac{3}{2}\times\dfrac{59}{14}-0\right]:\dfrac{3}{2}\)
\(=\dfrac{3}{2}\times\dfrac{59}{14}:\dfrac{3}{2}-0:\dfrac{3}{2}\)
\(=\dfrac{59}{14}-0\)
= \(\dfrac{59}{14}\)
Vì 1dm = 1/10m ; 1cm = 1/100m ; 1mm = 1/1000m nên ta có :
3dm = 3/10 m = 0,3 m ; 85cm = 85m = 0,85m ;
52mm = 52/1000 m = 0,052m.
3 dm = \(\frac{3}{10}\)m = 0,3 m
85 cm = \(\frac{85}{100}\)m = 0,85 m
52 mm = \(\frac{52}{100}\)m = 0,52 m
4.
a. 1/2 + 1/4 + 1/5
= 1*10/20 + 1*5/20 + 1*4/20
= (10 + 5 + 4)/20
= 19/20
= 0,95
b.1/2 * 4/5 : 1/4
= (1*4/2*5) : 1/4
= 4/10 : 1/4
= 2/5 * 4
= 8/5
= 1,6
\(\frac{14}{7}\):\(\frac{7}{34}\)x\(\frac{1}{8}\)
=\(\frac{14}{7}\)x\(\frac{34}{7}\)x\(\frac{1}{8}\)
=2x\(\frac{34}{7}\)x\(\frac{1}{8}\)
=\(\frac{68}{7}\)x\(\frac{1}{8}\)
=\(\frac{68}{56}\)=\(\frac{37}{28}\)
Hok tốt!