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a, \(\dfrac{7}{8}\) \(\times\) \(\dfrac{3}{13}\) + \(\dfrac{4}{9}\) \(\times\) \(\dfrac{4}{13}\)
= \(\dfrac{1}{13}\) \(\times\)( \(\dfrac{21}{8}\) + \(\dfrac{16}{9}\))
= \(\dfrac{1}{13}\) \(\times\)( \(\dfrac{189}{72}\) + \(\dfrac{128}{72}\))
= \(\dfrac{1}{13}\) \(\times\) \(\dfrac{317}{73}\)
= \(\dfrac{317}{949}\)
b, \(\dfrac{6}{5}\) + \(\dfrac{7}{3}\) + \(\dfrac{8}{9}\)
= \(\dfrac{54}{45}\) + \(\dfrac{105}{45}\) + \(\dfrac{40}{45}\)
= \(\dfrac{199}{45}\)
c, 23 : \(\dfrac{5}{14}\) + \(\dfrac{6}{7}\) + \(\dfrac{4}{9}\)
= \(\dfrac{322}{5}\) + \(\dfrac{6}{7}\) + \(\dfrac{4}{9}\)
= \(\dfrac{20286}{315}\) + \(\dfrac{270}{315}\) + \(\dfrac{140}{315}\)
= \(\dfrac{20696}{315}\)
d, 4\(\dfrac{1}{4}\) + 7\(\dfrac{3}{7}\) - 2\(\dfrac{4}{17}\)
= 4 + \(\dfrac{1}{4}\) + 7 + \(\dfrac{3}{7}\) - 2 - \(\dfrac{4}{17}\)
= (4+7-2) + (\(\dfrac{1}{4}\) + \(\dfrac{3}{7}\) - \(\dfrac{4}{17}\))
= 9 + \(\dfrac{119}{476}\) + \(\dfrac{204}{476}\) - \(\dfrac{112}{476}\)
= 9\(\dfrac{211}{476}\) = \(\dfrac{4495}{476}\)
e, 8 - (9\(\dfrac{2}{11}\) + \(\dfrac{8}{33}\))
= 8 - 9 - \(\dfrac{2}{11}\) - \(\dfrac{8}{33}\)
= -1 - \(\dfrac{2}{11}\) - \(\dfrac{8}{33}\)
= \(\dfrac{-33}{33}\) - \(\dfrac{-6}{33}\) - \(\dfrac{8}{33}\)
= - \(\dfrac{47}{33}\)
\(a,2\dfrac{2}{5}:y\times1\dfrac{3}{4}=\dfrac{7}{8}\\ \dfrac{12}{5}:y\times\dfrac{7}{4}=\dfrac{7}{8}\\ \dfrac{12}{5}:y=\dfrac{7}{8}:\dfrac{7}{4}\\ \dfrac{12}{5}:y=\dfrac{1}{2}\\ y=\dfrac{12}{5}:\dfrac{1}{2}=\dfrac{24}{5}\\ b,3\dfrac{2}{5}:y:1\dfrac{1}{4}=2\dfrac{3}{5}\\ \dfrac{17}{5}:y:\dfrac{5}{4}=\dfrac{13}{5}\\ y:\dfrac{5}{4}=\dfrac{17}{5}:\dfrac{13}{5}\\ y:\dfrac{5}{4}=\dfrac{17}{13}\\ y=\dfrac{17}{13}\times\dfrac{5}{4}=\dfrac{85}{52}\)
\(c,\dfrac{12}{5}-2\dfrac{2}{5}\times y=1\dfrac{1}{4}\\ \dfrac{12}{5}-\dfrac{12}{5}\times y=\dfrac{5}{4}\\ \dfrac{12}{5}\times y=\dfrac{12}{5}-\dfrac{5}{4}\\ \dfrac{12}{5}\times y=\dfrac{23}{20}\\ y=\dfrac{23}{20}:\dfrac{12}{5}\\ y=\dfrac{23}{48}\)
`@` `\text {Ans}`
`\downarrow`
`1,`
Ta có: `12 > 9 > 8 > 7`
`=> 12/8 > 9/8 > 8/8 > 7/8`
`=>` Phân số lớn nhất là `12/8`
`=> A.`
`2,`
So sánh \(\dfrac{3}{4}\text{ ; }\dfrac{9}{32}\)
\(\dfrac{3}{4}=\dfrac{3\times8}{4\times8}=\dfrac{24}{32}\)
Vì `24 > 9 `\(\Rightarrow\dfrac{24}{32}>\dfrac{9}{32}\) \(\Rightarrow\dfrac{3}{4}>\dfrac{9}{32}\)
\(\dfrac{9}{32}\text{;}\dfrac{3}{11}\)
\(\dfrac{9}{32}=\dfrac{9\times11}{32\times11}=\dfrac{99}{352}\)
\(\dfrac{3}{11}=\dfrac{3\times32}{11\times32}=\dfrac{96}{352}\)
Vì `99 > 96 \Rightarrow`\(\dfrac{99}{352}>\dfrac{96}{352}\Rightarrow\dfrac{9}{32}>\dfrac{3}{11}\)
Mà \(\dfrac{3}{11}< \dfrac{3}{4}\); \(\dfrac{9}{32}< \dfrac{3}{4}\)
`\Rightarrow`\(\dfrac{3}{4}>\dfrac{9}{32}>\dfrac{3}{11}\)
So sánh \(\dfrac{5}{7};\dfrac{3}{4}\)
\(\dfrac{5}{7}=\dfrac{5\times4}{7\times4}=\dfrac{20}{28}\)
\(\dfrac{3}{4}=\dfrac{3\times7}{4\times7}=\dfrac{21}{28}\)
Vì \(20< 21\Rightarrow\dfrac{20}{28}< \dfrac{21}{28}\Rightarrow\dfrac{5}{7}< \dfrac{3}{4}\)
So sánh \(\dfrac{5}{7};\dfrac{9}{32}\)
\(\dfrac{5}{7}=\dfrac{5\times32}{7\times32}=\dfrac{160}{224}\)
\(\dfrac{9}{32}=\dfrac{9\times7}{32\times7}=\dfrac{64}{224}\)
Vì \(160>64\Rightarrow\dfrac{160}{224}>\dfrac{64}{224}\Rightarrow\dfrac{5}{7}>\dfrac{9}{32}\)
`\Rightarrow` Thứ tự sắp xếp các phân số tăng dần là: \(\dfrac{3}{11};\dfrac{9}{32};\dfrac{5}{7};\dfrac{3}{4}\)
Bài 1 : A 12/8
Bài 2 : Theo thứ tự tăng dần là : 3/11, 9/32, 5/7, 3/4
` a/`
` 3 1/5 : 2 1/3 : y = 12/7 `
` 48/35 : y = 12/7 `
` y = 48/35 : 12/7 `
` y = 48/35 xx 7/12 `
` y = 4/5`
Vậy ` y = 4/5`
`b/`
` 3 : y xx 3 1/2 = 2/3 xx 3/4 `
` 3 : y xx 7/2 = 1/2`
` 3 : y = 1/2 : 7/2 `
` 3 : y = 1/2 xx 2/7 `
` 3 : y = 1/7 `
` y = 3 : 1/7 `
` y = 3 xx 7`
` y = 21 `
Vậy ` y = 21 `
`c/`
` 3 2/3 - y + 1 3/4 = 2`
` 11/3 - y + 7/4 = 2 `
` 11/3 -y = 2 - 7/4`
` 11/3 - y = 1/4 `
` y = 11/3 - 1/4 `
` y = 41/12 `
Vậy ` y = 41/12`
Bài 1:
Tổng của 2 số là
\(36\times2=72\)
Số lớn là
\(72-17=55\)
Bài 2:
a) \(4567+y\div34=10987\)
\(y\div34=10987-4567\)
\(y\div34=6420\)
\(y=6420\times34\)
\(y=218280\)
b) \(\dfrac{4}{3}+\dfrac{1}{2}\div y=2\)
\(\dfrac{1}{2}\div y=2-\dfrac{4}{3}\)
\(\dfrac{1}{2}\div y=\dfrac{2}{3}\)
\(y=\dfrac{1}{2}\div\dfrac{2}{3}\)
\(y=\dfrac{3}{4}\)
Bài 3:
a) \(\dfrac{2}{5}\times\dfrac{2}{5}+\dfrac{9}{8}\div3=\dfrac{4}{25}+\dfrac{9}{8}\times\dfrac{1}{3}=\dfrac{4}{25}+\dfrac{3}{8}=\dfrac{107}{200}\)
b) \(2-\left(\dfrac{1}{7}\times4+\dfrac{5}{21}\right)=2-\left(\dfrac{4}{7}+\dfrac{5}{21}\right)=2-\dfrac{17}{21}=\dfrac{25}{21}\)
Bài 1 : Gọi a là số lớn, b là số bé, theo đề bài ta có :
(a+b):2=36⇒a+b=72
mà b=17
Nên a=72-17=55
Bài 2 :
a) 4567+y:34=10987
⇒ y:34=10987-4567
⇒ y:34=6420
⇒ y=6420x34
⇒ y=218280
b) \(\dfrac{4}{3}+\dfrac{1}{2}:y=2\)
\(\Rightarrow\dfrac{1}{2}:y=2-\dfrac{4}{3}\)
\(\Rightarrow\dfrac{1}{2}:y=\dfrac{2}{3}\)
\(\Rightarrow y=\dfrac{1}{2}:\dfrac{2}{3}\)
\(\Rightarrow y=\dfrac{1}{2}x\dfrac{3}{2}\)
\(\Rightarrow y=\dfrac{3}{4}\)
Bài 3 :
\(\dfrac{2}{5}x\dfrac{2}{5}+\dfrac{9}{8}:3=\dfrac{4}{25}+\dfrac{9}{8}x\dfrac{1}{3}=\dfrac{4}{25}+\dfrac{3}{8}\)
= \(\dfrac{4x8}{25x8}+\dfrac{25x3}{25x8}=\dfrac{32}{200}+\dfrac{75}{200}=\dfrac{107}{200}\)
\(2-\left(\dfrac{1}{7}x4+\dfrac{5}{21}\right)=2-\left(\dfrac{4}{7}+\dfrac{5}{21}\right)=2-\left(\dfrac{12}{21}+\dfrac{5}{21}\right)=2-\dfrac{17}{21}=\dfrac{42}{21}-\dfrac{17}{21}=\dfrac{25}{21}\)
\(\dfrac{2}{5}\) x y : \(\dfrac{7}{4}\) = \(\dfrac{7}{8}\)
\(\dfrac{2}{5}\) x y = \(\dfrac{7}{8}\) x \(\dfrac{7}{4}\)
\(\dfrac{2}{5}\) x y = \(\dfrac{49}{32}\)
y = \(\dfrac{49}{32}\) : \(\dfrac{2}{5}\)
y = \(\dfrac{245}{64}\)
2\(\dfrac{2}{5}\): y x 1\(\dfrac{1}{4}\) = 2\(\dfrac{3}{5}\)
\(\dfrac{12}{5}\): y x \(\dfrac{5}{4}\) = \(\dfrac{13}{5}\)
\(\dfrac{12}{5}\): y = \(\dfrac{13}{5}\): \(\dfrac{5}{4}\)
\(\dfrac{12}{5}\): y = \(\dfrac{52}{25}\)
y = \(\dfrac{12}{5}\): \(\dfrac{52}{25}\)
y = \(\dfrac{15}{13}\)
Bài 4:
\(\dfrac{3}{4}+y:\dfrac{2}{5}=\dfrac{37}{16}\)
\(\Rightarrow y:\dfrac{2}{5}=\dfrac{37}{16}-\dfrac{3}{4}\)
\(\Rightarrow y:\dfrac{2}{5}=\dfrac{25}{16}\)
\(\Rightarrow y=\dfrac{2}{5}\cdot\dfrac{25}{16}\)
\(\Rightarrow y=\dfrac{5}{8}\)
________________
\(456+y:87=23987\)
\(\Rightarrow y:87=23987-456\)
\(\Rightarrow y:87=23531\)
\(\Rightarrow y=23531\cdot87\)
\(\Rightarrow y=2047197\)
a)\(\dfrac{4}{5}\times\dfrac{5}{8}:\dfrac{4}{5}\)
\(=\left(\dfrac{4}{5}:\dfrac{4}{5}\right)\times\dfrac{5}{8}\)
\(=1\times\dfrac{5}{8}=\dfrac{5}{8}\)
b)\(\dfrac{5}{6}+\left(\dfrac{1}{2}:\dfrac{3}{2}+\dfrac{4}{5}\right)\)
\(=\dfrac{5}{6}+\left(\dfrac{1}{3}+\dfrac{4}{5}\right)\)
\(=\dfrac{5}{6}+\dfrac{17}{15}\)
\(=\dfrac{59}{30}\)
Bài 2:
a) \(\dfrac{3}{4}+y:\dfrac{2}{5}=\dfrac{37}{16}\)
\(y:\dfrac{2}{5}=\dfrac{37}{16}-\dfrac{3}{4}\)
\(y:\dfrac{2}{5}=\dfrac{25}{16}\)
\(y=\dfrac{25}{16}\times\dfrac{2}{5}\)
\(y=\dfrac{5}{8}\)
b)\(456+y:87=23987\)
\(y:87=23987-456\)
\(y:87=23531\)
\(y=23531\times87\)
\(y=2047197\)
Giải:
\(9-3\times\left(x-9\right)=6\)
\(3\times\left(x-9\right)=9-6\)
\(3\times\left(x-9\right)=3\)
\(x-9=3:3\)
\(x-9=1\)
\(x=1+9\)
\(x=10\)
\(4+6\times\left(x+1\right)=70\)
\(6\times\left(x+1\right)=70-4\)
\(6\times\left(x+1\right)=66\)
\(x+1=66:6\)
\(x+1=11\)
\(x=11-1\)
\(x=10\)
\(\dfrac{x}{13}+\dfrac{15}{26}=\dfrac{46}{52}\)
\(\dfrac{x}{13}=\dfrac{23}{26}-\dfrac{15}{26}\)
\(\dfrac{x}{13}=\dfrac{4}{13}\)
\(\Rightarrow x=4\)
\(\dfrac{11}{14}-\dfrac{3}{x}=\dfrac{5}{14}\)
\(\dfrac{3}{x}=\dfrac{11}{14}-\dfrac{5}{14}\)
\(\dfrac{3}{x}=\dfrac{3}{7}\)
\(\Rightarrow x=7\)
\(5\times\left(3+7\times x\right)=40\)
\(3+7\times x=40:5\)
\(3+7\times x=8\)
\(7\times x=8-3\)
\(7\times x=5\)
\(x=5:7\)
\(x=\dfrac{5}{7}\)
\(x\times6+12:3=120\)
\(x\times6+4=120\)
\(x\times6=120-4\)
\(x\times6=116\)
\(x=116:6\)
\(x=\dfrac{58}{3}\)
\(x\times3,7+x\times6,3=120\)
\(x\times\left(3,7+6,3\right)=120\)
\(x\times10=120\)
\(x=120:10\)
\(x=12\)
\(\left(15\times24-x\right):0,25=100:\dfrac{1}{4}\)
\(\left(360-x\right):0,25=400\)
\(360-x=400.0,25\)
\(360-x=100\)
\(x=360-100\)
\(x=260\)
\(71+65\times4=\dfrac{x+140}{x}+260\)
\(\left(x+140\right):x+260=71+260\)
\(x:x+140:x+260=331\)
\(1+140:x+260=331\)
\(140:x=331-1-260\)
\(140:x=70\)
\(x=140:70\)
\(x=2\)
\(\left(x+1\right)+\left(x+4\right)+\left(x+7\right)+...+\left(x+28\right)=155\)
\(10\times x+\left(1+4+7+...+28\right)=155\)
Số số hạng \(\left(1+4+7+...+28\right)\) :
\(\left(28-1\right):3+1=10\)
Tổng dãy \(\left(1+4+7+...+28\right)\) :
\(\left(1+28\right).10:2=145\)
\(\Rightarrow10\times x+145=155\)
\(10\times x=155-145\)
\(10\times x=10\)
\(x=10:10\)
\(x=1\)
Đều theo cách lớp 5 nha em!
bài 1:
\(\dfrac{9}{5}\) = \(\dfrac{9.2}{5.2}\) = \(\dfrac{18}{10}\)
\(\dfrac{13}{25}\) = \(\dfrac{13.4}{25.4}\) = \(\dfrac{52}{100}\)
\(\dfrac{27}{300}\) = \(\dfrac{27:3}{300:3}\) = \(\dfrac{9}{100}\)
\(\dfrac{34}{200}\) = \(\dfrac{34:2}{200:2}\) = \(\dfrac{17}{100}\)
\(\dfrac{7}{8}\) = \(\dfrac{7.125}{8.125}\) = \(\dfrac{875}{1000}\)
bài 2: tìm y
a, y x \(\dfrac{6}{7}\) = \(\dfrac{12}{14}\)
y = \(\dfrac{12}{14}\): \(\dfrac{6}{7}\)
y = 1
b, \(\dfrac{52}{60}\) x y = \(\dfrac{4}{15}\)
y = \(\dfrac{4}{15}\): \(\dfrac{52}{60}\)
y = \(\dfrac{4}{13}\)
c, y: \(\dfrac{3}{4}\) = \(\dfrac{8}{12}\)
y = \(\dfrac{8}{12}\) x \(\dfrac{3}{4}\)
y = \(\dfrac{1}{2}\)
d, y : 6 = \(\dfrac{13}{18}\)
y = \(\dfrac{13}{18}\) x 6
y = \(\dfrac{13}{3}\)