Tính:
a) \(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}\) b) \(\dfrac{2}{9}+\dfrac{5}{9}+\dfrac{8}{9}\)
c) \(\dfrac{13}{14}-\dfrac{5}{14}-\dfrac{1}{14}\) d) \(\dfrac{7}{11}-\dfrac{4}{11}-\dfrac{3}{11}\)
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: \(=\dfrac{\dfrac{4}{36}-\dfrac{30}{36}-\dfrac{144}{36}}{\dfrac{21}{36}-\dfrac{1}{36}-\dfrac{360}{36}}=\dfrac{-160}{-340}=\dfrac{8}{17}\)
1) \(\dfrac{5}{13}\) +\(\dfrac{-5}{17}\) + \(\dfrac{-20}{41}\) + \(\dfrac{8}{13}\) +\(\dfrac{-21}{41}\)
2) \(\dfrac{1}{5}\) + \(\dfrac{-2}{9}\) + \(\dfrac{-7}{9}\) + \(\dfrac{4}{5}\) +\(\dfrac{16}{17}\)
3) \(\dfrac{2}{3.5}\) + \(\dfrac{2}{5.7}\) +\(\dfrac{2}{7.9}\) +....................+ \(\dfrac{2}{99.101}\)
1: =5/13+8/13-20/41-21/41-5/17
=1-1-5/17=-5/17
2: =1/5+4/5-2/9-7/9+16/17
=16/17+1-1=16/17
3: =1/3-1/5+1/5-1/7+...+1/99-1/101
=1/3-1/101
=98/303
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 3: Tính nhanh:
a) \(15\dfrac{3}{13}\)-\(\left(3\dfrac{4}{7}+8\dfrac{3}{13}\right)\)
b) \(\left(7\dfrac{4}{9}+4\dfrac{7}{11}\right)\)-\(3\dfrac{4}{9}\)
c) \(\dfrac{-7}{9}\).\(\dfrac{4}{11}\)+\(\dfrac{-7}{9}\).\(\dfrac{7}{11}\)+\(5\dfrac{7}{9}\)
d) 50%.\(1\dfrac{1}{3}\).10.\(\dfrac{7}{35}\).0,75
e) \(\dfrac{3}{1.4}\)+\(\dfrac{3}{4.7}\)+\(\dfrac{3}{7.10}\)+...+\(\dfrac{3}{40.43}\)
\(a,15\dfrac{3}{13}-\left(3\dfrac{4}{7}+8\dfrac{3}{13}\right)=15\dfrac{3}{13}-3\dfrac{4}{7}-8\dfrac{3}{13}=\left(15\dfrac{3}{13}-8\dfrac{3}{13}\right)-\dfrac{25}{7}=7-\dfrac{25}{7}=\dfrac{49}{7}-\dfrac{25}{7}=\dfrac{24}{7}\)
\(b,\left(7\dfrac{4}{9}+4\dfrac{7}{11}\right)-3\dfrac{4}{9}=\left(7\dfrac{4}{9}-3\dfrac{4}{9}\right)+4\dfrac{4}{9}=4+\dfrac{40}{9}=\dfrac{36}{9}+\dfrac{40}{9}=\dfrac{76}{9}\)
\(c,\dfrac{-7}{9}.\dfrac{4}{11}+\dfrac{-7}{9}.\dfrac{7}{11}+5\dfrac{7}{9}=\dfrac{-7}{9}\left(\dfrac{4}{11}+\dfrac{7}{11}\right)+\dfrac{52}{9}=\dfrac{-7}{9}.1+\dfrac{52}{9}=\dfrac{-7}{9}+\dfrac{52}{9}=\dfrac{45}{9}=5\)
\(d,50\%.1\dfrac{1}{3}.10.\dfrac{7}{35}.0,75=\dfrac{1}{2}.\dfrac{4}{3}.10.\dfrac{1}{5}.\dfrac{3}{4}=\left(\dfrac{1}{2}.\dfrac{1}{5}.10\right).\left(\dfrac{4}{3}.\dfrac{3}{4}\right)=1.1=1\)
\(e,\dfrac{3}{1.4}+\dfrac{3}{4.7}+...+\dfrac{3}{40.43}=1-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{7}+...+\dfrac{1}{40}-\dfrac{1}{43}=1-\dfrac{1}{43}=\dfrac{42}{43}\)
Tính (hợp lí nếu có thể)
\(\dfrac{1}{3}\) - \(\dfrac{3}{5}\) + \(\dfrac{5}{7}\) - \(\dfrac{7}{9}\) + \(\dfrac{9}{11}\) - \(\dfrac{11}{13}\) + \(\dfrac{13}{15}\) + \(\dfrac{11}{13}\) - \(\dfrac{9}{11}\) + \(\dfrac{7}{9}\) - \(\dfrac{5}{7}\) + \(\dfrac{3}{5}\) - \(\dfrac{1}{3}\)
\(\dfrac{1}{3}-\dfrac{3}{5}+\dfrac{5}{7}-\dfrac{7}{9}+\dfrac{9}{11}-\dfrac{11}{13}+\dfrac{13}{15}+\dfrac{11}{13}-\dfrac{9}{11}+\dfrac{7}{9}-\dfrac{5}{7}+\dfrac{3}{5}-\dfrac{1}{3}\)
\(=\left(\dfrac{1}{3}-\dfrac{1}{3}\right)-\left(\dfrac{3}{5}-\dfrac{3}{5}\right)+\left(\dfrac{5}{7}-\dfrac{5}{7}\right)-\left(\dfrac{7}{9}-\dfrac{7}{9}\right)+\left(\dfrac{9}{11}-\dfrac{9}{11}\right)-\left(\dfrac{11}{13}-\dfrac{11}{13}\right)+\dfrac{13}{15}\)
\(=\dfrac{13}{15}\)
Thực hiện phép tính ( tính nhanh nếu có thể )
a, -5/21 + -2/21 + 8/24
b, 4/11 . -2/7 + 4/11 . -4/7 + 4/11 . -1/7
c, \(10\dfrac{5}{9}\) - ( \(3\dfrac{5}{7}\) + \(4\dfrac{5}{9}\) )
d, 1/3 + \(1\dfrac{3}{4}\) - ( \(1\dfrac{3}{4}\) - 80% )
e, \(5\dfrac{3}{5}\) + \(7\dfrac{21}{48}\) : 10/7 - \(5\dfrac{21}{48}\) : 10/7
f, -5/7 . 2/11 - 5/11 . 9/7 + \(2\dfrac{5}{7}\)
g, -3/13 . 6/8 + 7/13 . -3/8 + \(1\dfrac{3}{8}\)
a: =-1/3+1/3=0
b: \(=\dfrac{4}{11}\left(-\dfrac{2}{7}-\dfrac{4}{7}-\dfrac{1}{7}\right)=\dfrac{4}{11}\cdot\left(-1\right)=-\dfrac{4}{11}\)
c: \(=10+\dfrac{5}{9}-3-\dfrac{5}{7}-4-\dfrac{5}{9}=3-\dfrac{5}{7}=\dfrac{16}{7}\)
d: \(=\dfrac{1}{3}+\dfrac{7}{4}-\dfrac{7}{4}+\dfrac{4}{5}=\dfrac{1}{3}+\dfrac{4}{5}=\dfrac{5+12}{15}=\dfrac{17}{15}\)
a: =-1/3+1/3=0
b: =10+59−3−57−4−59=3−57=167=10+59−3−57−4−59=3−57=167
d:
12+3/7-11+3/7 tính bằng cách thuận tiện nhé
bài 1:thực hiện phiép tính
a)\(\dfrac{7}{4}\)+\(\dfrac{3}{2}\)+\(\dfrac{-9}{16}\)
b)\(\dfrac{-2}{7}\)+\(\dfrac{3}{5}\)+\(\dfrac{9}{7}\)+\(\dfrac{-18}{5}\)
c)\(\left\{-\dfrac{5}{13}\right\}\)+\(\dfrac{11}{10}\)-\(\dfrac{-9}{10}\)+\(\dfrac{-8}{13}\)
bài 2:tìm x biết
a)\(\dfrac{2}{9}\)-x=\(\dfrac{-5}{9}\)
b)x+\(\dfrac{-7}{13}\)=\(\dfrac{1}{2}\)
2:
a: 2/9-x=-5/9
=>x=2/9+5/9=7/9
b: x-7/13=1/2
=>x=1/2+7/13=27/26
câu a
\(\dfrac{7}{4}+\dfrac{3}{2}+\dfrac{-9}{16}\\ =\dfrac{28}{16}+\dfrac{24}{16}-\dfrac{9}{16}=\dfrac{43}{16}\)
câu b
\(-\dfrac{2}{7}+\dfrac{3}{5}+\dfrac{9}{7}+\dfrac{-18}{5}\\ =-\dfrac{10}{35}+\dfrac{21}{35}+\dfrac{45}{35}-\dfrac{126}{35}\\ =-\dfrac{70}{35}=-2\)
câu c
\(-\dfrac{5}{13}+\dfrac{11}{10}-\dfrac{-9}{10}+\dfrac{-8}{13}\\ =-\dfrac{5}{13}+\dfrac{11}{10}+\dfrac{9}{10}-\dfrac{8}{13}\\ =-\dfrac{50}{130}+\dfrac{143}{130}+\dfrac{117}{130}-\dfrac{80}{130}\\ =\dfrac{130}{130}=1\)
bài 2
câu a
\(\dfrac{2}{9}-x=-\dfrac{5}{9}\\ x=\dfrac{2}{9}-\dfrac{-5}{9}\\ x=\dfrac{7}{9}\)
câu b
\(x+\dfrac{-7}{13}=\dfrac{1}{2}\\ x=\dfrac{1}{2}-\dfrac{-7}{13}\\ x=\dfrac{13}{26}+\dfrac{14}{26}\\ x=\dfrac{17}{26}\)
Thực hiện phép tính ( tính nhanh nếu có thể )
a)\(\dfrac{4}{11}.\dfrac{2}{5}+\dfrac{4}{5}.\dfrac{9}{11}+\dfrac{5}{6}\)
b)\(2\dfrac{1}{2}.60\%-\left(\dfrac{3}{7}+0,15\right):\dfrac{3}{10}\)
c)\(15\dfrac{3}{13}-\left(3\dfrac{4}{7}+8\dfrac{3}{13}\right)\)
d)\(\dfrac{-7}{9}.\dfrac{4}{11}+\dfrac{-7}{9}.\dfrac{7}{11}+5\dfrac{7}{9}\)
e)\(50\%.1\dfrac{1}{3}.10.\dfrac{7}{35}.0,75\)
a: \(=\dfrac{4\cdot2+4\cdot9}{55}+\dfrac{5}{6}=\dfrac{4}{5}+\dfrac{5}{6}=\dfrac{49}{30}\)
b: \(=\dfrac{3}{2}\cdot\dfrac{3}{5}-\left(\dfrac{3}{7}+\dfrac{3}{20}\right)\cdot\dfrac{10}{3}\)
\(=\dfrac{9}{10}-\dfrac{81}{140}\cdot\dfrac{10}{3}\)
\(=\dfrac{9}{10}-\dfrac{27}{14}=\dfrac{-36}{35}\)
c: \(=15+\dfrac{3}{13}-3-\dfrac{4}{7}-8-\dfrac{3}{13}\)
\(=4-\dfrac{4}{7}=\dfrac{24}{7}\)
d: \(=\dfrac{-7}{9}\left(\dfrac{4}{11}+\dfrac{7}{11}\right)+5+\dfrac{7}{9}=5\)
Bài 1 . Thực hiện phép tính sau :
a. \(\dfrac{-4}{11}\). \(\dfrac{7}{9}\)+\(\dfrac{-4}{11}\) . \(\dfrac{2}{9}\) - \(\dfrac{7}{11}\)
b. \(\dfrac{3}{5}\):\(\dfrac{-7}{10}\)+ 0,5 - \(\left(-\dfrac{9}{14}\right)\)
c. \(\dfrac{3}{5}\)-\(\dfrac{8}{5}\): (5,25+75%)
Bài 2 . Tìm x :
a) x - \(\dfrac{1}{2}\)= \(\dfrac{-1}{10}\) b.\(\dfrac{2}{3}x\) - \(\dfrac{7}{6}\)=\(\dfrac{5}{2}\) c)2,5 - \(\left(\dfrac{1}{8}x+\dfrac{1}{2}\right)\) =\(\dfrac{3}{4}\)
Mik làm Bài 2 nhé ~
Bài 2 :
a) \(x-\dfrac{1}{2}=-\dfrac{1}{10}\)
\(x=-\dfrac{1}{10}+\dfrac{1}{2}\)
\(x=\dfrac{2}{5}\)
b) \(\dfrac{2}{3}x-\dfrac{7}{6}=\dfrac{5}{2}\)
\(\dfrac{2}{3}x=\dfrac{5}{2}+\dfrac{7}{6}\)
\(\dfrac{2}{3}x=\dfrac{11}{3}\)
\(x=\dfrac{11}{3}:\dfrac{2}{3}\)
\(x=\dfrac{11}{3}.\dfrac{3}{2}\)
\(x=\dfrac{11}{2}\)
c) \(2,5-\left(\dfrac{1}{8}x+\dfrac{1}{2}\right)=\dfrac{3}{4}\)
\(\left(\dfrac{1}{8}x+\dfrac{1}{2}\right)=2,5-\dfrac{3}{4}\)
\(\left(\dfrac{1}{8}x+\dfrac{1}{2}\right)=\dfrac{5}{2}-\dfrac{3}{4}\)
\(\dfrac{1}{8}x+\dfrac{1}{2}=\dfrac{7}{4}\)
\(\dfrac{1}{8}x=\dfrac{7}{4}-\dfrac{1}{2}\)
\(\dfrac{1}{8}x=\dfrac{5}{4}\)
\(x=10\)
Bài 1:
a) \(\dfrac{-4}{11}.\dfrac{7}{9}+\dfrac{-4}{11}.\dfrac{2}{9}-\dfrac{7}{11}\)
\(=\dfrac{-4}{11}.\left(\dfrac{7}{9}+\dfrac{2}{9}\right)-\dfrac{7}{11}\)
\(=\dfrac{-4}{11}.1-\dfrac{7}{11}\)
\(=\dfrac{-4}{11}-\dfrac{7}{11}\)
\(=-1\)
b) \(\dfrac{3}{5}:\dfrac{-7}{10}+0,5-\left(\dfrac{-9}{14}\right)\)
\(=\dfrac{-6}{7}+\dfrac{1}{2}+\dfrac{9}{14}\)
\(=\dfrac{2}{7}\)
c) \(\dfrac{3}{5}-\dfrac{8}{5}:\left(5,25+75\%\right)\)
\(=\dfrac{3}{5}-\dfrac{8}{5}:\left(\dfrac{21}{4}+\dfrac{3}{4}\right)\)
\(=\dfrac{3}{5}-\dfrac{8}{5}:6\)
\(=\dfrac{3}{5}-\dfrac{4}{15}\)
\(=\dfrac{1}{3}\)
Bài 2:
a) \(x-\dfrac{1}{2}=\dfrac{-1}{10}\)
\(x=\dfrac{-1}{10}+\dfrac{1}{2}\)
\(x=\dfrac{2}{5}\)
b) \(\dfrac{2}{3}x-\dfrac{7}{6}=\dfrac{5}{2}\)
\(\dfrac{2}{3}x=\dfrac{5}{2}+\dfrac{7}{6}\)
\(\dfrac{2}{3}x=\dfrac{11}{3}\)
\(x=\dfrac{11}{3}:\dfrac{2}{3}\)
\(x=\dfrac{11}{2}\)
c) \(2,5-\left(\dfrac{1}{8}x+\dfrac{1}{2}\right)=\dfrac{3}{4}\)
\(\dfrac{1}{8}x+\dfrac{1}{2}=\dfrac{5}{2}-\dfrac{3}{4}\)
\(\dfrac{1}{8}x+\dfrac{1}{2}=\dfrac{7}{4}\)
\(\dfrac{1}{8}x=\dfrac{7}{4}-\dfrac{1}{2}\)
\(\dfrac{1}{8}x=\dfrac{5}{4}\)
\(x=\dfrac{5}{4}:\dfrac{1}{8}\)
\(x=10\)
