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\(a,=\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}=\dfrac{45}{10}=4,5\\ b,=\dfrac{4}{5}\times\left(\dfrac{3}{8}+\dfrac{5}{8}-\dfrac{7}{8}\right)\times2=\dfrac{8}{5}\times\dfrac{1}{8}=\dfrac{1}{5}=0,2\)
a) Rút gọn các phân số về tối giản, ta được:
\(\dfrac{1}{10}\)+\(\dfrac{2}{10}\)+\(\dfrac{3}{10}\)+\(\dfrac{4}{10}\)+\(\dfrac{5}{10}\)+\(\dfrac{6}{10}\)+\(\dfrac{7}{10}\)+\(\dfrac{8}{10}\)+\(\dfrac{9}{10}\)= kết quả là \(\dfrac{45}{10}\) ra số thập phân = \(4,5\)
b) \(\dfrac{4}{5}\) \(\times\) \(\left(\dfrac{3}{8}+\dfrac{5}{8}-\dfrac{7}{8}\right)\) = \(\dfrac{4}{5}\times\dfrac{1}{8}\) = \(\dfrac{4}{40}=\dfrac{1}{10}\)\(\div\dfrac{1}{2}\)
= \(\dfrac{2}{10}=0,2\)
`a,3/10=0,3`
`3/100=0,03`
`4 25/100=4 1/4=4,25`
`2002/1000=2,002`
`b,1/4=0,25`
`3/5=0,6`
`7/8=0,875`
`1 1/2=1,5`
a) \(\dfrac{1}{10}=0,1\)
\(\dfrac{1}{100}=0,01\)
\(\dfrac{1}{1000}=0,001\)
\(\dfrac{1}{10000}=0,0001\)
b) \(\dfrac{84}{10}=8,4\)
\(\dfrac{225}{100}=2,25\)
\(\dfrac{6453}{100}=64,53\)
\(\dfrac{25789}{10000}=2,5789\)
\(\dfrac{15}{10}=1,5;\dfrac{35}{100}=0,35;\dfrac{107}{100}=1,07\)
\(\dfrac{22109}{1000}=22,109;\dfrac{14}{5}=\dfrac{28}{10}=2,8;\dfrac{920}{1000}=0,92\)
\(\dfrac{138}{100}=1,38;\dfrac{2007}{10}=200,7;\dfrac{1}{1000}=0,001\)
1,5
0,35
1,007
22,109
2,8
0,92
1,38
200,7
0,001
\(\dfrac{4}{5}+x=3\dfrac{1}{5}\)
\(\Leftrightarrow\dfrac{4}{5}+x=\dfrac{16}{5}\)
\(\Leftrightarrow0,8+x=3,2\)
\(\Leftrightarrow x=3,2-0,8\)
\(\Leftrightarrow x=2,4\)
\(\dfrac{4}{5}+x=3\dfrac{1}{5}\)
⇔ \(\dfrac{4}{5}+x=\dfrac{16}{5}\)
⇔ \(x=\dfrac{12}{5}=2,4\)
\(a.\)
\(0.3=\dfrac{3}{10}\)
\(0.72=\dfrac{72}{100}\)
\(1.5=\dfrac{15}{10}\)
\(9.347=\dfrac{9347}{1000}\)
\(b.\)
\(\dfrac{1}{2}=\dfrac{5}{10}\)
\(\dfrac{2}{5}=\dfrac{4}{10}\)
\(\dfrac{3}{4}=\dfrac{75}{100}\)
\(\dfrac{6}{25}=\dfrac{24}{100}\)
a) \(0,3=\dfrac{3}{10}\)
\(0,72=\dfrac{72}{100}\)
\(1,5=\dfrac{15}{10}\)
\(9,347=\dfrac{9347}{1000}\)
b) \(\dfrac{1}{2}=\dfrac{5}{10}\)
\(\dfrac{2}{5}=\dfrac{4}{10}\)
\(\dfrac{3}{4}=\dfrac{75}{100}\)
\(\dfrac{6}{25}=\dfrac{24}{100}\)
a) \(A=\dfrac{3}{4}.\dfrac{8}{9}.\dfrac{15}{16}.\dfrac{24}{25}.....\dfrac{120}{121}.\dfrac{143}{144}\)
= \(\dfrac{1.3.2.4.3.5.4.6....10.12.11.13}{2^2.3^2.4^2.5^2...11^2.12^2}\)
= \(\dfrac{1.2.12.13}{2^2.12^2}=\dfrac{13}{2.12}=\dfrac{13}{24}\)
b) \(B=\dfrac{5}{9}.\dfrac{21}{25}.\dfrac{45}{49}.\dfrac{77}{81}....\dfrac{357}{361}.\dfrac{437}{441}\)
= \(\dfrac{1.5.3.7.5.9.7.11.....17.21.19.23}{3^2.5^2.7^2....19^2.21^2}=\dfrac{1.3.21.23}{3^2.21^2}\)
= \(\dfrac{23}{3.21}=\dfrac{23}{63}\)
Ta có:
\(\dfrac{1}{10}+\dfrac{4}{20}+\dfrac{9}{30}+\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\\ =\dfrac{1}{10}+\dfrac{2\times2}{10\times2}+\dfrac{3\times3}{10\times3}+\dfrac{4\times4}{10\times4}+\dfrac{5\times5}{10\times5}+\dfrac{6\times6}{10\times6}+\dfrac{7\times7}{10\times7}+\dfrac{8\times8}{10\times8}+\dfrac{9\times9}{10\times9}\\ =\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\\ =\dfrac{1+2+3+4+5+6+7+8+9}{10}\\ =\dfrac{45}{10}=4,5\)