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

\(3dm=\frac{3}{10}m=0,3m\)

\(85cm=\frac{85}{100}m=0,85m\)

\(52mm=\frac{52}{1000}m=0,052m\)

1 đúng nhé!

\(\frac{14}{7}\):\(\frac{7}{34}\)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!

\(\frac{8}{9}\):\(\frac{3}{4}\).\(\frac{5}{8}\)

=\(\frac{8}{9}\).\(\frac{4}{3}\).\(\frac{5}{8}\)

=\(\frac{8.4.5}{9.3.8}\)

=\(\frac{160}{216}\)

=0,(740)

a)

\(5dm=\dfrac{5}{10}m=0.5m\)

\(15cm=\dfrac{15}{100}m=0.15m\)

b) 

\(1h12'=1\dfrac{1}{5}h=\dfrac{6}{5}h\)

\(2h15'=2\dfrac{1}{4}h=\dfrac{9}{4}h\)

a,5 dm=\(\dfrac{5}{10}m=0,5m\);\(15cm=\dfrac{15}{100}m=0,15m\).

b,\(1h12p=1\dfrac{1}{5}h=\dfrac{6}{5}h\);\(2h15p=2\dfrac{1}{4}h=\dfrac{9}{4}h\).

`a) 1/2 + 1/4 + 1/5`
`=10/20 + 5/20 + 4/20`
`= 19/20`

`b)1/2xx 4/5 : 1/4`
`= 4/10 : 1/4`
`= 8/5`

a) 5hm = 5 100 km = 0,5km       

b) 12dam = 12 100 km = 0,12km

c) 64m = 64 1000 km= 0,064km  

d)  7dm = 7 10000  km = 0,007km

a) 5hm = 5 100 km = 0,5km

b) 12dam = 12 100 km = 0,12km

c) 64m = 64 100 km= 0,064km

d)  7dm = 7 10000  km = 0,007km