Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
\(\begin{array}{l}a)\dfrac{{10}}{{16}}:\dfrac{4}{{21}} = \dfrac{{10}}{{16}}.\dfrac{{21}}{4} = \dfrac{{105}}{{32}} = 105:32;\\b)1,3:2,75 = \dfrac{{1,3}}{{2,75}} = \dfrac{{130}}{{275}} = \dfrac{{26}}{{55}} = 26:55;\\c)\dfrac{{ - 2}}{5}:0,25 = \dfrac{{ - 2}}{5}:\dfrac{1}{4} = \dfrac{{ - 2}}{5}.\dfrac{4}{1} = \dfrac{{ - 8}}{5} = ( - 8):5\end{array}\)
Bài 1 : Ta thấy
\(\dfrac{10}{15}=\dfrac{2}{3};\dfrac{14}{21}=\dfrac{2}{3}\Rightarrow10:15=14:21\Rightarrow\dfrac{10}{15}=\dfrac{14}{21}\)
\(\dfrac{16}{\left(-4\right)}=-4;\dfrac{12}{\left(-3\right)}=-4\Rightarrow16:\left(-4\right)=12:\left(-3\right)\Rightarrow\dfrac{16}{\left(-4\right)}=\dfrac{12}{\left(-3\right)}=-4\)
\(\dfrac{\left(-5\right)}{15}=\dfrac{\left(-1,2\right)}{3,6}=-\dfrac{1}{3}\Rightarrow\left(-5\right):15=\left(-1,2\right):3,6\)
\(\dfrac{2}{3}:\dfrac{1}{4}=\dfrac{2}{3}.4=\dfrac{8}{3};\dfrac{16}{9}:\dfrac{16}{24}=\dfrac{16}{9}.\dfrac{24}{16}=\dfrac{8}{3}\)
\(\Rightarrow\left(\dfrac{2}{3}:\dfrac{1}{4}\right)=\left(\dfrac{16}{9}:\dfrac{16}{24}\right)=\dfrac{8}{3}\)
Bài 2 :
a) \(14.15=10.21\Rightarrow\dfrac{14}{10}=\dfrac{21}{15}=\dfrac{7}{5}\)
b) \(0,2.4,5=0,6.1,5\Rightarrow\dfrac{0,2}{0,6}=\dfrac{1,5}{4,5}=\dfrac{1}{3}\)
a) \(2.04:\left(-3.12\right)=\dfrac{204}{-312}=\dfrac{-17}{26}\)
b) \(\left(-1\dfrac{1}{2}\right):1.25=\dfrac{-3}{2}:\dfrac{5}{4}=\dfrac{-3}{2}\cdot\dfrac{4}{5}=\dfrac{-12}{10}=\dfrac{-6}{5}\)
c) \(4:5\dfrac{3}{4}=4:\dfrac{23}{4}=4\cdot\dfrac{4}{23}=\dfrac{16}{23}\)
d) \(10\dfrac{3}{7}:5\dfrac{3}{14}=\dfrac{73}{7}:\dfrac{73}{14}=\dfrac{2}{1}\)
a: \(\dfrac{15}{21}=\dfrac{5}{7}=\dfrac{30}{42}\)
=>Lập được TLT
b: \(\dfrac{0.25}{1.25}=\dfrac{1}{5}< >\dfrac{1}{7}\)
=>KO lập được TLT
c: \(0.4:\left(1+\dfrac{2}{5}\right)=0.4:1.4=\dfrac{2}{7}< >\dfrac{3}{5}\)
=>Ko lập được TLT
d: \(\dfrac{3}{5}:\dfrac{1}{7}=\dfrac{21}{5}=< >21:\dfrac{1}{5}\)
=>Ko lập được TLT
e: \(4+\dfrac{1}{2}:7+\dfrac{1}{2}=4.5:7.5=\dfrac{3}{5}< >\dfrac{2.7}{4.7}\)
=>Ko lập được TLT
f: 1/4:1/9=9/4
1/2:2/9=9/4
=>1/4:1/9=1/2:2/9
=>Lập được TLT
g: 2/7:4/11=2/7*11/4=22/28=11/14
7/2:4/11=7/2*11/4=77/8<>11/14
=>Ko lập được TLT
h: 2/5:10/2=2/5*2/10=4/50=2/25
2/1:1/4=8<>2/25
=>Ko lập được TLT
i: 2/7:7/4=2/7*4/7=8/49
16/49:2=8/49=2/7:7/4
=>Lập được TLT
a)\(1,5:2,16=15:216=5:72\)
b)\(4\dfrac{2}{7}:\dfrac{3}{5}=\dfrac{30}{7}:\dfrac{3}{5}=\dfrac{30}{7}.\dfrac{5}{3}=\dfrac{50}{7}=50:7\)
c)\(\dfrac{\dfrac{2}{9}}{0,31}=\dfrac{2}{9}:\dfrac{31}{100}=\dfrac{2}{9}.\dfrac{100}{31}=\dfrac{31}{450}=31:450\)
Lời giải:
a.
\(1,5:2,16=\frac{15}{10}: \frac{216}{100}=\frac{3}{2}: \frac{54}{25}=\frac{3}{2}.\frac{25}{54}=\frac{25}{36}\)
b.
\(4\frac{2}{7}: \frac{3}{5}=\frac{30}{7}:\frac{3}{5}=\frac{30}{7}.\frac{5}{3}=\frac{50}{7}\)
c.
\(\frac{2}{9}: 0,3=\frac{2}{9}: \frac{3}{10}=\frac{2}{9}.\frac{10}{3}=\frac{20}{27}\)
\(7 : 21 = \dfrac{7}{{21}} = \dfrac{1}{3}\);
\(\dfrac{1}{5}:\dfrac{1}{2} = \dfrac{1}{5} .\dfrac{2}{1} = \dfrac{2}{5}\);
\(\dfrac{1}{4}:\dfrac{3}{4} = \dfrac{1}{4}.\dfrac{4}{3} = \dfrac{1}{3}\);
\( 1,1 : 3,2 = \dfrac{{1,1}}{{3,2}}=\dfrac{11}{32}\);
\(1 : 2,5 =\dfrac{1}{{2,5}}=\dfrac{10}{25}=\dfrac{2}{5}\).
Ta thấy có các tỉ số bằng nhau là :
+) \(\dfrac{1}{4}:\dfrac{3}{4}\) và \(7 : 21\) (vì cùng bằng \(\dfrac{1}{3}\)) nên ta có tỉ lệ thức : \(\dfrac{1}{4}:\dfrac{3}{4} = 7:21\).
+) \(\dfrac{1}{5}:\dfrac{1}{2}\) và \(1 : 2,5\) (vì cùng bằng \(\dfrac{2}{5}\)) nên ta có tỉ lệ thức : \(\dfrac{1}{5}:\dfrac{1}{2} = 1 : 2,5\).
a) \(3,7:4,5=\dfrac{3,7}{4,5}=\dfrac{37}{45}\)
b) \(2\dfrac{1}{3}:4\dfrac{2}{3}=\dfrac{7}{3}:\dfrac{14}{3}=\dfrac{7}{3}\times\dfrac{3}{14}=\dfrac{1}{2}\)
c) \(\dfrac{3}{8}:0,7=\dfrac{3}{8}:\dfrac{7}{10}=\dfrac{3}{8}\times\dfrac{10}{7}=\dfrac{15}{28}\)
d) \(5\dfrac{1}{7}:2\dfrac{1}{3}=\dfrac{36}{7}:\dfrac{7}{3}=\dfrac{36}{7}\times\dfrac{3}{7}=\dfrac{108}{49}\)
`a)10/16 : 4/21`
`=105/32`
`=105:32`
`b)1,3:2,75`
`=26/55`
`=26:55`
`c)[-2]/5:0,25`
`=[-8]/5`
`=-8:5`
`a,` \(\dfrac{10}{16}\div\dfrac{4}{21}=\dfrac{5}{8}\div\dfrac{4}{21}=\dfrac{105}{32}=105\div32\)
`b,` \(1,3\div2,75=\dfrac{13}{10}\div\dfrac{11}{4}=\dfrac{26}{55}=26\div55\)
`c,` \(-\dfrac{2}{5}\div0,25=-\dfrac{2}{5}\div\dfrac{1}{4}=-\dfrac{8}{5}=-8\div5\)