tính bằng cách thuận tiện nhất : 6/8 x 12/25 + 2/8 x 12/25 - 12/25
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30x25x7x8
=(30x7)x(25x8)
=210x200
=42000
75x8x12x14
=(75x12)x(8x14)
=900x112
=100800
A) =(30*7)*(25*8)
=210*200
=4200
B)=(75*8)*(12*14)
=600*168
=100800

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

1a) \(\frac{12}{17}+\frac{19}{17}+\frac{8}{17}\)
\(=\left(\frac{12}{17}+\frac{8}{17}\right)+\frac{19}{17}\)
\(=\frac{20}{17}+\frac{19}{17}\)
\(=\frac{39}{17}\)
b) \(\frac{2}{5}+\frac{7}{12}+\frac{13}{12}\)
\(=\frac{2}{5}+\frac{5}{3}\)
\(=\frac{31}{15}\)
2) \(\frac{25}{3}-x=\frac{5}{6}\)
\(x=\frac{25}{3}-\frac{5}{6}\)
\(x=\frac{45}{6}\)
ủng hộ tớ nha


a) \(...=-\dfrac{12}{46}-\dfrac{15}{21}+\dfrac{3}{7}-\dfrac{7}{23}\)
\(=-\dfrac{12}{46}-\dfrac{7}{23}-\dfrac{15}{21}+\dfrac{3}{7}\)
\(=-\dfrac{6}{23}-\dfrac{7}{23}-\dfrac{5}{7}+\dfrac{3}{7}\)
\(=-\dfrac{13}{23}-\dfrac{2}{7}\)
\(=-\dfrac{13.7}{23.7}-\dfrac{2.23}{23.7}\)
\(=-\dfrac{91}{161}-\dfrac{46}{161}=-\dfrac{137}{161}\)
b) \(...=-21+\dfrac{7}{9}-\dfrac{3}{17}+\dfrac{25}{9}\)
\(=-21-\dfrac{3}{17}+\dfrac{7}{9}+\dfrac{25}{9}\)
\(=-21-\dfrac{3}{17}+\dfrac{32}{9}\)
\(=-\dfrac{3213}{153}-\dfrac{27}{153}+\dfrac{544}{153}=-\dfrac{2696}{153}\)

\(\frac{30}{11}\times\frac{66}{25}\times\frac{75}{210}\)
\(=\frac{30\times6\times11\times3\times25}{11\times25\times30\times7}\)
\(=\frac{18}{7}\)
\(\left(\frac{8}{11}+\frac{3}{12}\right)+\frac{3}{11}\)
\(=\frac{8}{11}+\frac{3}{12}+\frac{3}{11}\)
\(=\left(\frac{8}{11}+\frac{3}{11}\right)+\frac{3}{12}\)
\(=1+\frac{3}{12}\)
\(=\frac{5}{4}\)
Matcha
\(\frac{30}{11}\times\frac{66}{25}\times\frac{75}{210}\)
\(=\frac{30\times66\times75}{11\times25\times210}\)
\(=\frac{1\times6\times3}{1\times1\times7}\)
\(=\frac{18}{7}\)
\(\left(\frac{8}{11}+\frac{3}{12}\right)+\frac{3}{11}\)
\(=\frac{8}{11}+\frac{3}{12}+\frac{3}{11}\)
\(=1+\frac{3}{12}\)
\(=1+\frac{1}{4}\)
\(=\frac{5}{4}\)
bằng 0
\(\dfrac{6}{8}\times\dfrac{12}{25}+\dfrac{2}{8}\times\dfrac{12}{25}-\dfrac{12}{25}\)
\(=\dfrac{12}{25}\times\left(\dfrac{6}{8}+\dfrac{2}{8}-1\right)\)
\(=\dfrac{12}{25}\times0=0\)