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49 x 37 = 37 x 49
(214 x 25) x 4 = 214 x (25 x 4)
103 x 18 + 103 x 12 = 103 x (18 + 12)
Bài 1:
a: \(=\dfrac{21}{7}\cdot\dfrac{15}{45}\cdot\dfrac{9}{18}=3\cdot\dfrac{1}{3}\cdot\dfrac{1}{2}=\dfrac{1}{2}\)
b: \(=\dfrac{11}{33}\cdot\dfrac{24}{8\cdot12}\cdot\dfrac{27}{9}=\dfrac{24}{96}=\dfrac{1}{4}\)
`a, 36 + 14 + 9`
`= 50 + 9`
`= 59`
`b, 51 + 12 + 18`
`=51 + 30`
`= 81`
`c, 65 + 9 + 5`
`= 70 + 9`
`= 79`
`d, 31 + 26 + 69`
`= 100 + 26`
`= 126`
6/7 + 5/8 = 83/56
36/12 - 5/3= 3 - 5/3 = 9/3 - 5/3 = 4/3
7/9 x 18/49 = 126/441 = 2/7
a: =8/5-2/3=24/15-10/15=14/15
12/20-6/18=3/5-1/3=9/15-5/15=4/15
b: 18/21-12/27=6/7-7/9=54/63-49/63=5/63
8/12-20/50=2/3-2/5=10/15-6/15=4/15
\(a,\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{8}{5}-\dfrac{2}{3}=\dfrac{14}{15}\\ \dfrac{12}{20}-\dfrac{6}{18}=\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{4}{15}\\ b,\dfrac{18}{21}-\dfrac{12}{27}=\dfrac{6}{7}-\dfrac{4}{9}=\dfrac{26}{63}\\ \dfrac{8}{12}-\dfrac{20}{50}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)
= 18*( 75+37-12)
=18*100
=1800
= 18 x (75+37-12)
= 18 x 100
=1800