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a: =7/12+6/36
=7/12+2/12=9/12=3/4
b: =8/9-2/3=8/9-6/9=2/9
c: \(=\dfrac{7\cdot2+5\cdot3}{18}\cdot\dfrac{3}{5}=\dfrac{29}{18}\cdot\dfrac{3}{5}=\dfrac{87}{90}=\dfrac{29}{30}\)
a) \(\dfrac{7}{12}+\dfrac{3}{4}\times\dfrac{2}{9}=\dfrac{7}{12}+\dfrac{6}{36}=\dfrac{7}{12}+\dfrac{2}{12}=\dfrac{9}{12}=\dfrac{3}{4}\)
b) \(\dfrac{8}{9}-\dfrac{4}{15}:\dfrac{2}{5}=\dfrac{8}{9}-\dfrac{4}{15}\times\dfrac{5}{2}=\dfrac{8}{9}-\dfrac{2}{3}=\dfrac{8}{9}-\dfrac{6}{9}=\dfrac{2}{9}\)
c) \(\left(\dfrac{7}{9}+\dfrac{5}{6}\right)\times\dfrac{3}{5}=\dfrac{29}{18}\times\dfrac{3}{5}=\dfrac{87}{90}=\dfrac{29}{30}\)
A =\(\frac{2}{5}\times\frac{4}{7}+\frac{3}{5}\times\frac{4}{7}\) B = \(\frac{17}{13}\times\frac{12}{17}-\frac{4}{13}\times\frac{12}{17}\) C = \(\frac{9}{14}:\frac{6}{7}+\frac{5}{14}:\frac{6}{7}\) D =\(\frac{9}{12}:\frac{7}{9}\times\frac{12}{19}\)
= \(\frac{4}{7}\times\left(\frac{2}{5}+\frac{3}{5}\right)\) =\(\left(\frac{17}{13}-\frac{4}{13}\right)\times\frac{12}{17}\) = \((\frac{9}{14}+\frac{5}{14}):\frac{6}{7}\) = \(\frac{9}{12}\times\frac{9}{7}\times\frac{12}{19}\)
=\(\frac{4}{7}\times1\) = \(1\times\frac{12}{17}\) = \(1:\frac{6}{7}\) = \(\frac{9\times9\times12}{12\times7\times19}\)
=\(\frac{4}{7}\) = \(\frac{12}{17}\) =\(\frac{7}{6}\) = \(\frac{9\times9}{7\times19}=\frac{81}{133}\)
a: \(=\left(\dfrac{4}{9}+\dfrac{5}{9}\right)+\left(\dfrac{1}{8}+\dfrac{7}{8}\right)=1+1=2\)
b: \(=\left(\dfrac{1}{6}+\dfrac{4}{6}+\dfrac{7}{6}\right)+\left(\dfrac{5}{12}+\dfrac{7}{12}\right)=2+1=3\)
câu a bằng 15/8
câu b bằng 19/6
câu c bằng 3/10
câu d bằng 27/4
a) 8 × 5 × 9 = (8 × 5) × 9 = 40 × 9 = 360
b) 6 × 7 × 5 = (6 × 5) × 7= 30 × 7= 210
c) 6 × 4 × 25 = 6 × (4 × 25) = 6 × 100= 600
1.a,=(54+45+1).113
=100.113
=11300
b,=(3/7+8/14)+(4/9+10/18)
=1+1
=2
2.a,=13/10+1/3
=49/30
b,=12/9.(1/12+1/6)
=12/9.1/4
=1/3
c,=3/4.3/2
=9/8
d,=3/2-1/3
=7/6
1:tính bằng cách thuận tiện nhất:
a)54 x 113 + 45 x 113 + 113
= 54 x 113 + 45 x 113 + 113x1
=113 x(54+45+1)
= 113x100
=1300
b)3/7 + 4/9 + 8/14 + 10/18
=(3/7+8/14)+(4/9+10/18)
= 1 + 1
=2
=( 1/12+9/12+2/12+1/12) + ( 2/7+5/7) + (10/20+9/20)
= 13/12 +1+19/20
đến đây bạn tự tính nha
5/9 x 3/8 = 15/72 = 5/24
5/6 + 9/12 : 13/8 = 5/6 + 9/12 x 8/13 = 5/6 + 6/13 = 65/78 + 36/78 = 101/78
5/9 x 3/8
= 5x3/9x8
= 15/72=5/26
5/6 + 9/12 : 13/8
= 5/6 + 72/156
= 91/78
a] 4/12 ; 5/12 ; 11/2 ; 1/4
b] 1 ; 9/12; 12/5 ; 11/3
c] 8/21; 6/11;8/7
d] 2/3 ;2/7 15/2
a]1/3 5/12 11/2 1/4
b]1 3/4 12/5 33/9
c]8/21 6/11 8/7
d]2/3 2/7 15/2
