Bài 1 : Tính
a) \(\dfrac{1}{3}.\dfrac{-4}{5}+\dfrac{1}{3}.\dfrac{-6}{5}\)
b) \(\dfrac{3}{7}.\dfrac{9}{26}-\dfrac{1}{14}.\dfrac{1}{13}\)
bài 1: Tính
a) \(\dfrac{-5}{7}\) . \(\dfrac{2}{11}\) + \(\dfrac{-5}{7}\) . \(\dfrac{9}{11}\) + 1\(\dfrac{5}{7}\)
b) \(\dfrac{-3}{14}\) +\(\dfrac{5}{8}\) -\(\dfrac{1}{2}\)
c) ( \(\dfrac{1}{4}\) +\(\dfrac{-5}{13}\))+( \(\dfrac{2}{11}\) + \(\dfrac{-8}{13}\) + \(\dfrac{3}{4}\) )
d) ( \(\dfrac{21}{31}\) + \(\dfrac{-16}{7}\) )+( \(\dfrac{44}{53}\) +\(\dfrac{10}{31}\) )+\(\dfrac{9}{53}\)
e) \(\dfrac{1}{9}\) - \(\dfrac{5}{6}\) -4
___________
\(\dfrac{7}{12}\) - \(\dfrac{1}{36}\) -10
giúp em
a: =-5/7(2/11+9/11)+12/7
=12/7-5/7
=7/7=1
b: \(=\dfrac{-12}{56}+\dfrac{35}{56}-\dfrac{28}{56}=\dfrac{-5}{56}\)
c: \(=\dfrac{1}{4}-\dfrac{5}{13}+\dfrac{2}{11}-\dfrac{8}{13}+\dfrac{3}{4}\)
=1-1+2/11
=2/11
d: \(=\dfrac{21}{31}+\dfrac{-16}{7}+\dfrac{44}{53}+\dfrac{10}{31}+\dfrac{9}{53}\)
=1+1-16/7
=-2/7
e: \(=\dfrac{\dfrac{4}{36}-\dfrac{30}{36}-\dfrac{144}{36}}{\dfrac{21}{36}-\dfrac{1}{36}-\dfrac{360}{36}}=\dfrac{-160}{-340}=\dfrac{8}{17}\)
Bài 1.( 2 điểm)Tính bằng cách hợp lí:
a) \(\dfrac{1}{2}+\dfrac{9}{10}+\dfrac{5}{6}-\dfrac{11}{14}-\dfrac{1}{3}+\dfrac{-4}{35}\)
b) \(\left(\dfrac{18}{23}+\dfrac{7}{12}\right)+\left(\dfrac{-13}{19}-\dfrac{3}{4}\right)+\left(\dfrac{-6}{19}+\dfrac{5}{23}\right)\)
c) \(\dfrac{4}{3}+\dfrac{-5}{6}+\dfrac{-1}{4}\)
d) \(\dfrac{5}{6}-\dfrac{7}{5}+\dfrac{17}{30}\)
1: \(\dfrac{1}{2}+\dfrac{9}{10}+\dfrac{5}{6}-\dfrac{11}{14}-\dfrac{1}{3}+\dfrac{-4}{35}\)
\(=\left(\dfrac{1}{2}+\dfrac{5}{6}-\dfrac{1}{3}\right)+\dfrac{9}{10}-\left(\dfrac{11}{14}+\dfrac{4}{35}\right)\)
\(=\dfrac{3+5-2}{6}+\dfrac{9}{10}-\dfrac{55+8}{70}\)
\(=1+\dfrac{9}{10}-\dfrac{9}{10}\)
=1
Bài 1 : Thực hiện phép tính
a/ \(\dfrac{7}{6}\) - \(\dfrac{13}{12}\) + \(\dfrac{3}{4}\)
b/ 1 \(\dfrac{1}{2}\) . \(\dfrac{-4}{5}\) + \(\dfrac{3}{10}\)
c/ \(\dfrac{25}{9}\) . \(\dfrac{3}{10}\) + ( \(\dfrac{-5}{3}\) )\(^2\) . \(\dfrac{7}{10}\) + | \(\dfrac{-25}{3}\) |
Bài 2 : Tìm x , biết
a/ x - \(\dfrac{5}{6}\) = \(\dfrac{1}{4}\)
b/ \(\dfrac{26}{x}\) = \(\dfrac{-13}{-15}\)
( Cần gấp )
a)\(\dfrac{7}{8}\)x\(\dfrac{3}{13}\)+\(\dfrac{4}{9}\)x\(\dfrac{4}{13}\)
b)\(\dfrac{6}{5}\)+\(\dfrac{7}{3}\)+\(\dfrac{8}{9}\)
c)23: \(\dfrac{5}{14}\)+\(\dfrac{6}{7}\)+\(\dfrac{4}{9}\)
d)\(4\dfrac{1}{4}\)+\(7\dfrac{3}{7}\)-\(2\dfrac{4}{17}\)
e)8-(9\(\dfrac{2}{11}\)+\(\dfrac{8}{33}\))
1. <, >, =
\(\dfrac{14}{7}\) ...... \(\dfrac{9}{7}\)
\(\dfrac{6}{13}\) ....... 1
\(\dfrac{7}{9}\)..........\(\dfrac{14}{18}\)
\(\dfrac{4}{9}\)........ \(\dfrac{26}{45}\)
\(\dfrac{11}{24}\)........ \(\dfrac{3}{8}\)
\(\dfrac{42}{91}\)....... \(\dfrac{7}{13}\)
\(\dfrac{34}{64}\)........... \(\dfrac{13}{16}\)
\(\dfrac{17}{30}\).......... \(\dfrac{8}{15}\)
2.
\(\dfrac{14}{7}>\dfrac{9}{7}\)
\(\dfrac{6}{13}< 1\)
\(\dfrac{7}{9}=\dfrac{14}{18}\)
\(\dfrac{4}{9}=\dfrac{20}{45}< \dfrac{26}{45}\)
\(\dfrac{11}{24}>\dfrac{9}{24}=\dfrac{3}{8}\)
\(\dfrac{42}{91}=\dfrac{42:7}{91:7}=\dfrac{6}{13}< \dfrac{7}{13}\)
\(\dfrac{34}{64}< \dfrac{52}{64}=\dfrac{13}{16}\)
\(\dfrac{17}{30}>\dfrac{16}{30}=\dfrac{8}{15}\)
bài 1)
a)(\(\dfrac{12}{42}\) - \(\dfrac{26}{91}\) ).(\(\dfrac{-4}{7}\) +\(\dfrac{-5}{9}\))
b) \(\dfrac{9}{13}\) . \(\dfrac{-12}{7}\) +\(\dfrac{9}{13}\) .\(\dfrac{29}{17}\)
c) \(\dfrac{4}{7}\) +\(\dfrac{6}{7}\) .\(\dfrac{1}{7}\) +\(\dfrac{1}{7}\) .\(\dfrac{8}{7}\)
d) (\(\dfrac{5}{7}\) + \(\dfrac{9}{7}\) ). \(\dfrac{7}{10}\) +(\(\dfrac{8}{7}\) + \(\dfrac{13}{7}\) ). \(\dfrac{7}{10}\)
a: =(2/7-2/7)(-4/7-5/9)=0
b:
Sửa đề: 9/13*(-12/17)+9/13*29/27
=9/13(-12/17+29/17)
=9/13*17/17=9/13
c: \(=\dfrac{1}{7}\left(4+\dfrac{6}{7}+\dfrac{8}{7}\right)=\dfrac{1}{7}\cdot6=\dfrac{6}{7}\)
d: =7/10(5/7+9/7+8/7+13/7)
=5*7/10=7/2
bài 3: tính bằng cách thuận tiện
a) \(\dfrac{13}{50}\) + 0,09 + \(\dfrac{41}{100}\) + 0,24 b) \(9\dfrac{1}{4}\) + \(6\dfrac{2}{7}\) + \(7\dfrac{3}{5}\) + \(8\dfrac{2}{3}\) + \(\dfrac{2}{5}\) + \(\dfrac{1}{3}\) + \(\dfrac{5}{7}\) + \(\dfrac{3}{4}\)
Bài 4: so sánh các cặp phân số sau:
a) \(\dfrac{2008}{2009}\) và \(\dfrac{10}{9}\) b) \(\dfrac{1}{a-1}\) và \(\dfrac{1}{a+1}\) (a>1)
Bài 5: cho phân số \(\dfrac{15}{39}\). Tìm 1 số tự nhiên, biết rằng khi thêm số đó vào mẫu số của phân số đã cho và giữ nguyên tử số thì được phân số mới bằng \(\dfrac{3}{11}\)
giải giúp mik vs, mik cần gấp!
Bài 3
a,26/100+0,009+41/100+0,24
0,26+0,09+0,41+0,24
(0,26+0,24)+(0,09+0,41)
0,5+0,5
=1
b,9+1/4+6+2/7+7+3/5+8+2/3+2/5+1/3+5/7+3/4
(9+6+7+8)+(2/7+5/7)+(1/4+3/4)+(3/5+2/5)+(2/3+1/3)
30+1+1+1+1
=34
Bài 4,5 khó quá mik ko bít lamf^^))
Bài 5: vì \(\dfrac{3}{11}\) = \(\dfrac{3\times5}{11\times5}\) = \(\dfrac{15}{55}\)
Vậy Khi giữ nguyên tử số thì số cần thêm vào mẫu số là:
55 - 39 = 16
Đáp số: 16
Bài 4: a, \(\dfrac{2008}{2009}\) < 1; \(\dfrac{10}{9}\) > 1
\(\dfrac{2008}{2009}\) < \(\dfrac{10}{9}\)
b, \(\dfrac{1}{a+1}\) và \(\dfrac{1}{a-1}\)
Ta có: a + 1 > a - 1 ⇒ \(\dfrac{1}{a+1}\) < \(\dfrac{1}{a-1}\)
Bài 1. Thực hiện phép tính:
a) |5.0,6+\(\dfrac{2}{3}\)|- \(\dfrac{1}{3}\)
b)(0,25 - 1\(\dfrac{1}{4}\)) : 5 - \(\dfrac{1}{5}\).(-3)\(^2\)
c)\(\dfrac{14}{17}.\dfrac{7}{5}-\dfrac{-3}{17}:\dfrac{5}{7}\)
d)\(\dfrac{7}{16}+\dfrac{-9}{25}+\dfrac{9}{16}+\dfrac{-16}{25}\)
e)\(\dfrac{5}{6}+2\sqrt{\dfrac{4}{9}}\)
a) Ta có: \(\left|5\cdot0.6+\dfrac{2}{3}\right|-\dfrac{1}{3}\)
\(=\left|3+\dfrac{2}{3}\right|-\dfrac{1}{3}\)
\(=3+\dfrac{2}{3}-\dfrac{1}{3}\)
\(=3+\dfrac{1}{3}=\dfrac{10}{3}\)
b) Ta có: \(\left(0.25-1\dfrac{1}{4}\right):5-\dfrac{1}{5}\cdot\left(-3\right)^2\)
\(=\left(\dfrac{1}{4}-\dfrac{5}{4}\right)\cdot\dfrac{1}{5}-\dfrac{1}{5}\cdot9\)
\(=\dfrac{-4}{4}\cdot\dfrac{1}{5}-\dfrac{1}{5}\cdot9\)
\(=\dfrac{1}{5}\cdot\left(-1-9\right)\)
\(=-10\cdot\dfrac{1}{5}=-2\)
c) Ta có: \(\dfrac{14}{17}\cdot\dfrac{7}{5}-\dfrac{-3}{17}:\dfrac{5}{7}\)
\(=\dfrac{14}{17}\cdot\dfrac{7}{5}-\dfrac{-3}{17}\cdot\dfrac{7}{5}\)
\(=\dfrac{7}{5}\cdot\left(\dfrac{14}{17}+\dfrac{3}{17}\right)\)
\(=\dfrac{7}{5}\cdot1=\dfrac{7}{5}\)
d) Ta có: \(\dfrac{7}{16}+\dfrac{-9}{25}+\dfrac{9}{16}+\dfrac{-16}{25}\)
\(=\left(\dfrac{7}{16}+\dfrac{9}{16}\right)-\left(\dfrac{9}{25}+\dfrac{16}{25}\right)\)
\(=\dfrac{16}{16}-\dfrac{25}{25}\)
\(=1-1=0\)
e) Ta có: \(\dfrac{5}{6}+2\sqrt{\dfrac{4}{9}}\)
\(=\dfrac{5}{6}+2\cdot\dfrac{2}{3}\)
\(=\dfrac{5}{6}+\dfrac{4}{3}\)
\(=\dfrac{5}{6}+\dfrac{8}{6}=\dfrac{13}{6}\)
Bài 1. Tính
A= \(\left(8\dfrac{2}{7}-4\dfrac{2}{7}\right)-3\dfrac{4}{9}\)
B= \(\left(10\dfrac{2}{9}-6\dfrac{2}{9}\right)+2\dfrac{3}{5}\)
Bài 2. Tính
a) \(5\dfrac{1}{2}.3\dfrac{1}{4}\) b) \(6\dfrac{1}{3}:4\dfrac{2}{9}\) c) \(4\dfrac{3}{7}.2\)
`A=(8 2/7-4 2/7)-3 4/9`
`=8+2/7-4-2/7-3-4/9`
`=4-3-4/9`
`=1-4/9=5/9`
`B=(10 2/9-6 2/9)+2 3/5`
`=10+2/9-6-2/9+2+3/5`
`=4+2+3/5`
`=6+3/5=33/5`
Bài 2:
`a)5 1/2*3 1/4`
`=11/2*13/4`
`=143/8`
`b)6 1/3:4 2/9`
`=19/3:38/9`
`=19/3*9/38=3/2`
`c)4 3/7*2`
`=31/7*2`
`=62/7`
Bài 1:
\(A=\left(8\dfrac{2}{7}-4\dfrac{2}{7}\right)-3\dfrac{4}{9}\)
\(A=\left(\dfrac{58}{7}-\dfrac{30}{7}\right)-\dfrac{31}{9}\)
\(A=4-\dfrac{31}{9}\)
\(A=\dfrac{5}{9}\)
\(B=\left(10\dfrac{2}{9}-6\dfrac{2}{9}\right)+2\dfrac{3}{5}\)
\(B=\left(\dfrac{92}{9}-\dfrac{56}{9}\right)+\dfrac{13}{5}\)
\(B=4+\dfrac{13}{5}\)
\(B=\dfrac{33}{5}\)
Bài 2:
a) \(5\dfrac{1}{2}.3\dfrac{1}{4}=\dfrac{11}{2}.\dfrac{13}{4}=\dfrac{11.13}{2.4}=\dfrac{143}{8}\)
b) \(6\dfrac{1}{3}:4\dfrac{2}{9}=\dfrac{19}{3}:\dfrac{38}{9}=\dfrac{19}{3}.\dfrac{9}{38}=\dfrac{3}{2}\)
c) \(4\dfrac{3}{7}.2=\dfrac{31}{7}.2=\dfrac{31.2}{7}=\dfrac{62}{7}\)