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\(\dfrac{2}{5}\) tấn = 1000 kg \(\times\) \(\dfrac{2}{5}\) = 400 kg
Vậy \(\dfrac{2}{5}\) tấn = 400 kg
\(\dfrac{3}{4}\) tạ = 100 kg \(\times\) \(\dfrac{3}{4}\) = 75 kg
Vậy \(\dfrac{3}{4}\) tạ = 75 kg
\(\dfrac{3}{4}\) giờ = \(60\) phút \(\times\) \(\dfrac{3}{4}\) = 45 phút
vậy \(\dfrac{3}{4}\) giờ = 45 phút
\(\dfrac{3}{5}\)m2 = 100 dm2 \(\times\) \(\dfrac{3}{5}\) = 60 dm2
Vậy \(\dfrac{3}{5}\) m2 = 60 dm2
\(\dfrac{1}{4}\) km2 = 1000000 m2 \(\times\) \(\dfrac{1}{4}\) = 250000 m2
Vậy \(\dfrac{1}{4}\) km2 = 250000 m2
\(\dfrac{2}{5}\) phút = 60 giây \(\times\) \(\dfrac{2}{5}\) = 24 giây
Vậy \(\dfrac{2}{5}\) phút = 24 giây
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\(\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{49.50}\)
\(=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{49}-\dfrac{1}{50}\)
\(=\dfrac{1}{2}-\dfrac{1}{50}=\dfrac{12}{25}\)
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2/
a)\(\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{4}{11}+\dfrac{7}{11}\)
= \(\dfrac{5}{5}+\dfrac{11}{11}\)
= \(1+1\)
= \(2\)
b) \(\left(\dfrac{1}{8}+\dfrac{3}{8}\right)+\left(\dfrac{4}{12}+\dfrac{5}{12}\right)\)
= \(\dfrac{4}{8}+\dfrac{8}{12}\)
= \(\dfrac{12}{24}+\dfrac{16}{24}\)
= \(\dfrac{28}{24}\)
= \(\dfrac{7}{6}\)
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1)1 dm2 =..0,01....m2
2)1 cm2 =..0,0001....m2
3)1 km2=....1000000...m2
4)1 dm2 =...100...cm2
5)3 km2 =...3000000........m2
6)25 m2 =..2500......dm2
1) 0,01 m2
2) 0,0001 m2
3) 1 000 000 m2
4) 100 cm2
5) 3 000 000 m2
6) 2500 dm2
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Bài 1:
Chiều rộng hcn đó là:
\(\dfrac{4}{3}\times\dfrac{1}{2}=\dfrac{2}{3}\) ( m )
Chu vi hình chữ nhật đó là:
\(\left(\dfrac{4}{3}+\dfrac{2}{3}\right)\times2=4\left(m\right)\)
Đ/s: 4 m
Bài 2:
\(\dfrac{2}{5}+\dfrac{1}{3}:\dfrac{2}{3}=\dfrac{2}{5}+\dfrac{1}{3}\times\dfrac{3}{2}=\dfrac{2}{5}+\dfrac{1}{2}=\dfrac{4}{10}+\dfrac{5}{10}=\dfrac{9}{10}\)
Bài 3;
\(\Rightarrow\dfrac{3}{4}+x\times\dfrac{5}{2}=\dfrac{37}{16}\\ \Rightarrow x\times\dfrac{5}{2}=\dfrac{37}{16}-\dfrac{3}{4}=\dfrac{25}{16}\\ \Rightarrow x=\dfrac{25}{16}\times\dfrac{2}{5}=\dfrac{5}{8}\)
Bài 4:
\(\dfrac{1}{2}+\dfrac{1}{4}+\dfrac{1}{8}+\dfrac{1}{16}=\dfrac{15}{16}\)
Bài 5:
\(\Rightarrow x\times\dfrac{2}{5}=\dfrac{4}{7}\\ \Rightarrow x=\dfrac{4}{7}\times\dfrac{5}{2}=\dfrac{10}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
2/5*3/4=3/10
3/10:1/2=3/5
Vậy m =3