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Bài 1:
a: x+1/2=5/6
nên x=5/6-1/2=1/3
b: x+1/4=3/4
nên x=3/4-1/4=2/4=1/2
c: x+3/10=1/2
nên x=1/2-3/10=5/10-3/10=1/5
d: x+1/4=3/8
nên x=3/8-1/4=3/8-2/8=1/8
A) 5/4 x X = 3/8 + 5/12
5/4 x X = 19/24
X = 19/24 : 5/4
X = 19/30
vậy x =...
B, 3 x 7/10 + 7/10 x 5 + 2 x 7/10
= 7/10 x ( 3 + 5 + 2)
= 7/10 x 10
= 7
\(\dfrac{2}{5}:x=\dfrac{7}{10}\)
\(x=\dfrac{2}{5}:\dfrac{7}{10}=\dfrac{2}{5}\cdot\dfrac{10}{7}\)
\(x=\dfrac{2\cdot5\cdot2}{5\cdot7}\)
\(x=\dfrac{4}{7}\)
x:3/4 = 5/6
x = 5/8
b) x -2/3 = 4/6 = 2/3
x = 4/3
c) 7/10 : x = 7/2
x = 1/5
d) 5/8 : x = 5
x = 1/8
X : 3/4=5/6
X=5/6x3/4
X=5/8
X - 2/3=4/6
X=4/6+2/3
X=4/3
7/10 : X=7/2
X=7/10:7/2
X=1/5
5/8 : X= 5
X=5/8:5
X=1/8
K MK NHAAA
a, \(\frac{2}{3}:\frac{5}{7}:\frac{x}{9}=\frac{2}{7}:\frac{3}{5}:\frac{10}{9}\Leftrightarrow\frac{2\times7\times9}{3\times5\times x}=\frac{2\times5\times9}{7\times3\times10}\Leftrightarrow\frac{42}{5\times x}=\frac{3}{7}\Leftrightarrow294=15\times x\Leftrightarrow x=19,6\)
Các phần sau tương tự.
Dùng phương pháp nhân chéo và kiểm tra trình độ tính toán, khả năng rút gọn.
Thay kết quả vào x để kiểm tra lại bài.
a)
x + 2/5 = 1/2
x = 1/2 - 2/5
x = 1/10
b)
x + 3/7 = 2/5 + 3/10
x + 3/7 = 7/10
x = 7/10 - 3/7
x = 19/70
c)
19/20 - x = 8/5 - 3/4
19/20 - x = 17/20
x = 19/20 - 17/20
x = 1/5
a) x + 2/5 = 1/2
x = 1/2 - 2/5
x = 3/10
b) x + 3/7 = 2/5 + 3/10
x + 3/7 = 7/10
x = 7/10 - 3/7
x = 19/70
c) 19/20 - x = 8/5 - 3/4
19/20 - x = 17/20
x = 19/20 - 17/20
x = 2/20 = 1/10
Bài 1: Tính
a, 1/2 x 2/3 x 3/4 = 1/4
b, 7/8 x 8/9 x 9/10 = 7/10
c, 5/14 x 7/15 x 28/7 = 2/3
d, 2 x 1/2 x 3 x 1/3 x 4 x 1/4 x 5 x 1/5 = 1
Bài 2: Tính
a, 7/20 - ( 5/8 - 3/5 ) = 7/20 - 1/40 = 14/40 - 1/40 = 13/40
b, 5/6 + ( 5/9 - 1/4 ) = 5/6 + 11/36 = 30/36 + 11/36 = 41/36
c, 9/10 - ( 2/5 + 3/10 ) + 7/20 = 9/10 - 7/10 + 7/20 = 2/10 + 7/20 = 4/20 + 7/20 = 11/20.
Bài 3: Tìm x:
a, 1/2 + x = 5/6
x = 5/6 - 1/2
x = 1/3
b, 5/6 - x = 1/3
x = 5/6 - 1/3
x = 1/2
c, x - 1/mấy vậy bạn
d, 1/3 x x = 1/6
x = 1/6 : 1/3
x = 1/2
\(\dfrac{45}{135}=\dfrac{45:45}{135:45}=\dfrac{1}{3}\)
\(\dfrac{117}{234}=\dfrac{117:117}{234:117}=\dfrac{1}{2}\)
\(\dfrac{1515}{2727}=\dfrac{1515:303}{2727:303}=\dfrac{5}{9}\)
\(\dfrac{232323}{494949}=\dfrac{232323:10101}{494949:10101}=\dfrac{23}{49}\)
\(\left(x-\dfrac{1}{3}\right)+\dfrac{1}{4}=\dfrac{1}{2}\)
\(x-\dfrac{1}{3}=\dfrac{1}{2}-\dfrac{1}{4}\)
\(x-\dfrac{1}{3}=\dfrac{2}{4}-\dfrac{1}{4}\)
\(x-\dfrac{1}{3}=\dfrac{1}{4}\)
\(x=\dfrac{1}{4}+\dfrac{1}{3}\)
\(x=\dfrac{3}{12}+\dfrac{4}{12}\)
\(x=\dfrac{7}{12}\)
\(x-\left(\dfrac{1}{7}+\dfrac{2}{5}\right)=\dfrac{16}{35}\)
\(x-\left(\dfrac{5}{35}+\dfrac{14}{35}\right)=\dfrac{16}{35}\)
\(x-\dfrac{19}{35}=\dfrac{16}{35}\)
\(x=\dfrac{16}{35}+\dfrac{19}{35}\)
\(x=\dfrac{35}{35}\)
\(x=1\)
\(x+\dfrac{3}{7}=\dfrac{2}{5}+\dfrac{3}{10}\)
\(x+\dfrac{3}{7}=\dfrac{4}{10}+\dfrac{3}{10}\)
\(x+\dfrac{3}{7}=\dfrac{7}{10}\)
\(x=\dfrac{7}{10}-\dfrac{3}{7}\)
\(x=\dfrac{49}{70}-\dfrac{30}{70}\)
\(x=\dfrac{19}{30}\)
2/5 : x = 7/10
x = 2/5 : 7/10
x = 4/7
HT
X = 4/7