Khái niệm số thập phân

`2,60 ha = 2,6 ha`

`2ha 600 m^2 = 26 ha`

`0,206 km^2 = 2060 ha`

`20600 m^2 = 2,06 ha`

`2060 m^2 = 0,206 ha`

`-> 20600 = 2,06 ha`

`a, 2,5 km^2 = 2500000 m^2`

`b, 10,4 ha = 104000 m^2`

`c, 0,03 ha = 300 m^2`

`d, 800 dm^2 = 8 m^2`

`e, 80 dm^2 = 0,8 m^2`

`g, 918 dm^2 = 9,18 m^2`

a) 856cm²

b) 42dm²

c) 18000m²

d)10m²

e) 6390dm²= 639000cm²

g) 2,7dm²= 270cm²

\(a.15735m^2=1,5735ha\)

\(b.892m^2=0,0892ha\)

\(c.428ha=4,28km^2\)

\(d.14ha=0,14km^2\)

a) 15735 m2 = 1,5735  ha

b) 892 m2 = 0,0892  ha 

c) 428 ha = 4,28 km2

d) 14 ha = 0,14 km2

a: =9/12+4/12+4/12=17/12

b: =3/7x4/12=12/84=1/7

c: =28/16-7/16-14/16=7/16

d: =15/18x8/3x3/4=15/18x2=5/6x2=5/3

\(a,\dfrac{3}{4}+\dfrac{1}{3}+\dfrac{4}{12}=\dfrac{3}{4}+\dfrac{1}{3}+\dfrac{1}{3}=\dfrac{3}{4}+\left(\dfrac{1}{3}+\dfrac{1}{3}\right)=\dfrac{3}{4}+\dfrac{2}{3}=\dfrac{9}{12}+\dfrac{8}{12}=\dfrac{17}{12}\)

\(b,\dfrac{3}{2}\times\dfrac{2}{7}\times\dfrac{4}{12}=\dfrac{3}{7}\times\dfrac{4}{12}=\dfrac{1}{7}\)

\(c,\dfrac{7}{4}-\dfrac{7}{16}-\dfrac{7}{8}=\dfrac{28}{16}-\dfrac{7}{16}-\dfrac{14}{16}=\dfrac{1}{2}\)

\(d,\dfrac{15}{18}:\dfrac{3}{8}\times\dfrac{3}{4}=\dfrac{15}{18}\times\dfrac{8}{3}\times\dfrac{3}{4}=\dfrac{15\times8\times3}{18\times3\times4}=\dfrac{5}{3}\)

các phân số thập phân là

\(\dfrac{41}{100};\dfrac{2}{10};\dfrac{3}{1000};\dfrac{7}{700}=\dfrac{1}{100}\)

a) \(\dfrac{13}{5}=2,6\)

\(\dfrac{4}{25}=0,16\)

\(\dfrac{3}{4}=0,75\)

b) \(\dfrac{75}{100}=\dfrac{3}{4}=0,75\)

\(\dfrac{102}{600}=\dfrac{17}{100}=0,17\)

\(\dfrac{62}{125}=0,496\)

13/5 -> 26/10 -> 2,6

4/25 -> 16/100 -> 0,16

3/4 -> 75/100 -> 0,75

75/500 -> 15/100 -> 0,15

102/600 -> 17/100 -> 0,17

62/125 -> 496/1000 -> 0,496

a/

\(\dfrac{13}{5}=\dfrac{26}{10}=2,6\\ \dfrac{4}{25}=\dfrac{16}{100}=0,16\\ \dfrac{3}{4}=\dfrac{75}{100}=0,75\)

b/

\(\dfrac{75}{500}=\dfrac{15}{100}=0,15\\ \dfrac{102}{600}=\dfrac{17}{100}=0,17\\ \dfrac{62}{125}=\dfrac{496}{1000}=0,496\)

\(\dfrac{1}{1000}+\dfrac{13}{1000}+\dfrac{25}{1000}+...+\dfrac{109}{1000}\)

\(=\dfrac{1+13+25+...+109}{1000}\)

\(=\dfrac{\left(109+1\right)\times10:2}{1000}\)

\(=\dfrac{500}{1000}=\dfrac{1}{2}\)

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