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a. 1/3 + 5/3 = 6/3=2 ; 9/12 - 1/3 = 9/12 - 4/12 = 5 / 12 ; 5/12 + 1/3= 5/12 + 4/12 = 9/12 = 3/4 ; 9/12 - 5/12 = 4/12= 1/3
b. 2*3*4 / 2*4*3*5 = 24/120= 4/60 = 1/15 ; mh ko hieu 2 cau cuoi
Bn tu nghi not nhe
0o0 Chuc ban hoc gioi 0o0
\(\frac{1\times2\times3\times4}{5\times6\times7\times8}\times X=1\)\(1\)
\(\frac{1}{70}\) \(\times X\)\(=1\)
\(X\) \(=1:\frac{1}{70}\)
\(X\) \(=70\)
a) x : ( 12 x 15 ) = 8/3 x 4 x 15
x : 180 = 160
x = 160 : 180
x = 8/9
Vậy x = 8/9
b) ( 1/2 x 2/3 x 3/4 x 4/5 ) : x = 1 x 2 x 3 x 4/ 5 x 6 x 7 x 8
1/5 : x = 1/70
x = 1/5 : 1/70
x = 14
Vậy x = 14
a: \(=\dfrac{2}{5}\cdot\dfrac{5}{6}\cdot\dfrac{3}{4}\cdot\dfrac{4}{3}=\dfrac{2}{6}=\dfrac{1}{3}\)
b: \(=\dfrac{123\cdot145+100}{123\cdot145+12\cdot145-45}=\dfrac{123\cdot145+100}{123\cdot145+1695}\)
=3587/3906
\(\frac{1}{1.2.3}+\frac{1}{2.3.4}+\frac{1}{3.4.5}+.......+\frac{1}{8.9.10}\)
\(=\frac{1}{2}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+\frac{2}{3.4.5}+......+\frac{2}{8.9.10}\right)\)
\(=\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+\frac{1}{3.4}-\frac{1}{4.5}+.......+\frac{1}{8.9}-\frac{1}{9.10}\right)\)
\(=\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{9.10}\right)=\frac{1}{2}.\left(\frac{1}{2}-\frac{1}{90}\right)=\frac{1}{2}.\frac{22}{45}=\frac{11}{45}\)
a) 160 b) 1612,8 c) 1960 d) 0,25
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