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câu 1:
a 3/11 - 7/11 + 2/11 = 3 - 7 + 2 / 11
= -5 + 2/11
= -3/11
b 7/15 - 2/3 = 7/15 - 10/15
= -1/5
c 3/5.9/11 + 3/5.2/11 - 2 1/2
= 3/5.9/11 + 3/5.2/11 - 5/2
= 3/5.( 9/11 + 2/11 - 5/2 )
= 3/5.( 1 - 5/2 )
= 3/5 . -3/2
= -9/10
câu 2
a. x + 75% = 5/12
x + 3/4 = 5/12
x = 5/12 - 3/4
x = -1/3
vậy x = -1/3
b.| x - 7/15 | = 3/10
x - 7/15 = 3/10 => x = 3/10 + 7/15 => x = 23/30
x - 7/15 = -3/10 => x = -3/10 + 7/15 => x = 1/6
vậy x = 23/30 hoặc 1/6
tk mk nhé mk làm đc nửa bài rùi
Câu 1 :
a) \(\frac{3}{11}-\frac{7}{11}+\frac{2}{11}=\frac{-4}{11}+\frac{2}{11}=\frac{-2}{11}\)
b) \(\frac{7}{15}+\frac{2}{3}=\frac{7}{15}+\frac{10}{15}=\frac{17}{15}\)
c) \(\frac{3}{5}.\frac{9}{11}+\frac{3}{5}.\frac{2}{11}-2\frac{1}{2}\)
\(=\left(\frac{3}{5}.\frac{9}{11}+\frac{3}{5}.\frac{2}{11}\right)-\frac{5}{2}\)
\(=\frac{3}{5}.\left(\frac{9}{11}+\frac{2}{11}\right)-\frac{5}{2}\)
\(=\frac{3}{5}.1-\frac{5}{2}\)
\(=\frac{3}{5}-\frac{5}{2}=\frac{6}{10}-\frac{25}{10}=\frac{-19}{10}=-1\frac{9}{10}\)
Câu 2 :
a) \(x+75\%=\frac{5}{12}\)
\(x+\frac{3}{4}=\frac{5}{12}\)
\(x=\frac{5}{12}-\frac{3}{4}\)
\(x=\frac{5}{12}-\frac{9}{12}=\frac{-4}{12}=\frac{-1}{3}\)
Vậy : \(x=\frac{-1}{3}\)
Câu 3 :
Giải :
Số HS trung bình là :
\(48.\frac{5}{12}=20\left(HS\right)\)
Số HS còn lại là :
\(48-20=28\)\(\left(HS\right)\)
Số HS khá là :
\(28.\frac{4}{7}=16\left(HS\right)\)
Số HS giỏi là :
\(28-16=12\left(HS\right)\)
Đ/S : 12 Học sinh
câu
a= -1
b=(3/5-3/4):25%
=-3/20:25%
=-0,6
c)(3/4+-14/4).8/11
=-11/4.8/11= -2
d) -3/7.(2/11+9/11).10/7
=1
B1
a) \(1-\left(5\frac{3}{8}+x-7\frac{5}{24}\right):16\frac{2}{3}=0\)
\(1-\left(\frac{43}{8}+x-\frac{173}{24}\right):\frac{50}{3}=0\)
\(1-\left(x-\frac{11}{6}\right).\frac{3}{50}=0\)
\(\left(x-\frac{11}{6}\right).\frac{3}{50}=1-0\)
\(\left(x-\frac{11}{6}\right).\frac{3}{50}=1\)
\(x-\frac{11}{6}=1:\frac{3}{50}\)
\(x-\frac{11}{6}=\frac{50}{3}\)
\(x=\frac{50}{3}+\frac{11}{6}\)
\(x=\frac{37}{2}\)
b) \(\frac{3}{5}+\frac{5}{7}:x=\frac{1}{3}\)
\(\frac{5}{7}:x=\frac{1}{3}-\frac{3}{5}\)
\(\frac{5}{7}:x=-\frac{4}{15}\)
\(x=\frac{5}{7}:\left(-\frac{4}{15}\right)\)
\(x=-\frac{75}{28}\)
c) \(\left(4\frac{1}{2}-\frac{2}{5}.x\right):\frac{7}{4}=\frac{11}{9}\)
\(\left(\frac{9}{2}-\frac{2}{5}.x\right):\frac{7}{4}=\frac{11}{9}\)
\(\frac{9}{2}-\frac{2}{5}.x=\frac{11}{9}.\frac{7}{4}\)
\(\frac{9}{2}-\frac{2}{5}.x=\frac{11}{2}\)
\(\frac{2}{5}.x=\frac{9}{2}-\frac{11}{2}\)
\(\frac{2}{5}.x=-1\)
\(x=-1:\frac{2}{5}\)
\(x=-\frac{5}{2}\)
B2
a) \(\left(\frac{1}{2}+\frac{1}{3}+\frac{2}{6}\right).24:5-\frac{9}{22}:\frac{15}{121}\)
\(=\left(\frac{3}{6}+\frac{2}{6}+\frac{2}{6}\right).24:5-\frac{9}{22}.\frac{121}{15}\)
\(=\frac{7}{6}.24:5-\frac{33}{10}\)
\(=28:5-\frac{33}{10}\)
\(=\frac{28}{5}-\frac{33}{10}\)
\(=\frac{56}{10}-\frac{33}{10}\)
\(=\frac{23}{10}\)
b) \(\frac{5}{14}+\frac{18}{35}+\left(1\frac{1}{4}-\frac{5}{4}\right):\left(\frac{5}{12}\right)^2\)
\(=\frac{25}{70}+\frac{36}{70}+\left(\frac{5}{4}-\frac{5}{4}\right):\frac{25}{144}\)
\(=\frac{61}{70}+0:\frac{25}{144}\)
\(=\frac{61}{70}+0\)
\(=\frac{61}{70}\)