Bài 5: ( Đề 1) Viết các PS sau thành PS thập phân
a) \(\dfrac{3}{25}\) =.............................. b) \(\dfrac{7}{8}\) =................................
c) \(\dfrac{9}{45}\) =..............................
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
Bài 1:
a)
\(\dfrac{1}{2}=\dfrac{1\times6}{2\times6}=\dfrac{6}{12}\)
\(\dfrac{2}{3}=\dfrac{2\times4}{3\times4}=\dfrac{8}{12}\)
\(\dfrac{3}{4}=\dfrac{3\times3}{4\times3}=\dfrac{9}{12}\)
b)
\(\dfrac{1}{3}=\dfrac{1\times15}{3\times15}=\dfrac{15}{45}\)
\(\dfrac{2}{15}=\dfrac{2\times3}{15\times3}=\dfrac{6}{45}\)
\(\dfrac{4}{45}\) (giữ nguyên)
c)
\(\dfrac{1}{8}=\dfrac{1\times3}{8\times3}=\dfrac{3}{24}\)
\(\dfrac{2}{3}=\dfrac{2\times8}{3\times8}=\dfrac{16}{24}\)
\(\dfrac{5}{2}=\dfrac{5\times12}{2\times12}=\dfrac{60}{24}\)
d)
\(\dfrac{2}{7}=\dfrac{2\times4}{7\times4}=\dfrac{8}{28}\)
\(\dfrac{9}{4}=\dfrac{9\times7}{4\times7}=\dfrac{63}{28}\)
\(\dfrac{5}{28}\) (giữ nguyên)
Bài 2:
a)
\(4=\dfrac{4}{1}=\dfrac{4\times12}{1\times12}=\dfrac{48}{12}\)
\(\dfrac{9}{4}=\dfrac{9\times3}{4\times3}=\dfrac{27}{12}\)
b)
\(\dfrac{5}{8}=\dfrac{5\times30}{8\times30}=\dfrac{150}{240}\)
\(\dfrac{25}{30}=\dfrac{5}{6}=\dfrac{5\times40}{6\times40}=\dfrac{200}{240}\)
\(2=\dfrac{2}{1}=\dfrac{2\times240}{1\times240}=\dfrac{480}{240}\).
4\(\dfrac{1}{2}\)=4,5 3\(\dfrac{4}{5}\)=3,8 2\(\dfrac{3}{4}\)=2,75 1\(\dfrac{12}{25}\)=1,48.
4 1/2=4,5
3 4/5=3,8
2 3/4=2,75
1 12/25=1,48
đúng 100% nha
`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) Thứ tự từ bé đến lớn: \(\dfrac{2}{7};\dfrac{3}{7};\dfrac{5}{7}\)
b) Thứ tự từ bé đến lớn: \(\dfrac{1}{8};\dfrac{5}{8};\dfrac{7}{8}\)
c) Thứ tự từ bé đến lớn: \(\dfrac{1}{10};\dfrac{7}{10};\dfrac{9}{10}\)
\(A=\dfrac{10n-3}{5n+2}=\dfrac{10n+4-7}{5n+2}=\dfrac{2\left(5n+2\right)-7}{5n+2}=2-\dfrac{7}{5n+2}\)
Để A nguyên thì \(7\) ⋮ 5n + 2
\(\Rightarrow5n+2\inƯ\left(7\right)=\left\{1;-1;7;-7\right\}\)
\(\Rightarrow5n\in\left\{-1;-3;5;-9\right\}\)
\(\Rightarrow n\in\left\{-\dfrac{1}{5};-\dfrac{3}{5};1;-\dfrac{9}{5}\right\}\)
________________
\(B=\dfrac{12n+5}{6n-3}=\dfrac{12n-6+11}{6n-3}=\dfrac{2\left(6n-3\right)+11}{6n-3}=2+\dfrac{11}{6n-3}\)
Để B nguyên thì \(11\) ⋮ 6n - 3
\(\Rightarrow6n-3\inƯ\left(11\right)=\left\{1;-1;11;-11\right\}\)
\(\Rightarrow6n\in\left\{4;2;14;-8\right\}\)
\(\Rightarrow n\in\left\{\dfrac{2}{3};\dfrac{1}{3};\dfrac{7}{3};-\dfrac{4}{3}\right\}\)
Những phân số bằng nhau là:
\(\dfrac{15}{60}\)=\(\dfrac{3}{12}\)
\(\dfrac{-7}{5}\)=\(\dfrac{28}{-20}\)
\(\dfrac{3}{25}=\dfrac{3\times4}{25\times4}=\dfrac{12}{100}\\ \dfrac{7}{8}=\dfrac{7\times125}{8\times125}=\dfrac{875}{1000}\\ \dfrac{9}{45}=\dfrac{9:9}{45:9}=\dfrac{1}{5}=\dfrac{1\times2}{5\times2}=\dfrac{2}{10}\)
a) 12/100
b) 875/1000
c) 18/100