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a) 3/7+5/2+4/7
=(3/7+4/7)+5/2
=1+5/2
=7/2
b)6/8+4/5+1/4
=(6/8+1/4)+4/5
=1+4/5
=9/5
đến đó thôi mệt quá
a; \(\dfrac{3}{7}\) + \(\dfrac{5}{2}\) + \(\dfrac{4}{7}\)
= (\(\dfrac{3}{7}+\dfrac{4}{7}\)) + \(\dfrac{5}{2}\)
= 1 + \(\dfrac{5}{2}\)
= \(\dfrac{2}{2}+\dfrac{5}{2}\)
= \(\dfrac{7}{2}\)
b; \(\dfrac{6}{8}\) + \(\dfrac{4}{5}\) + \(\dfrac{1}{4}\)
= \(\dfrac{1}{4}\) + \(\dfrac{4}{5}\) + \(\dfrac{1}{4}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{1}{4}\)) + \(\dfrac{4}{5}\)
= \(\dfrac{2}{4}\) + \(\dfrac{4}{5}\)
= \(\dfrac{1}{2}\) + \(\dfrac{4}{5}\)
= \(\dfrac{5}{10}\) + \(\dfrac{8}{10}\)
= \(\dfrac{13}{10}\)
21+22+23+24+25+26+9+8+7+6+5+4 =180
mình thấy rồng con lon ton làm đúng đấy
\(\dfrac{21}{16}\times\dfrac{8}{5}\times\dfrac{15}{7}=\dfrac{21\times8\times15}{16\times5\times7}=\dfrac{7\times3\times8\times5\times3}{8\times2\times5\times7}=\dfrac{3\times3}{2}=\dfrac{9}{2}\)
\(\dfrac{18}{9}\times\dfrac{9}{36}\times\dfrac{27}{3}=2\times\dfrac{1}{4}\times9=\dfrac{1}{2}\times9=\dfrac{9}{2}\)
a, = \(\frac{11}{21}\)x \(\left(\frac{7}{4}+\frac{5}{4}\right)\)
= \(\frac{11}{21}\)x 3
= \(\frac{33}{21}\)
b) = \(\left(\frac{23}{14}-\frac{9}{14}\right)\)x \(\frac{6}{13}\)
= 1 x \(\frac{6}{13}\)
= \(\frac{6}{13}\)
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a)70=2*5*7
=>2*3*5/70=3/7
b)33*4=11*3*2*2=11*6*2
=>2*6*11/33*4=1
c)21*45=9*5*3*7
=>21*45/3*5*7*9=1
\(\frac{2\times3\times5}{70}\)
= \(\frac{2\times3\times5}{7\times2\times5}\)
= \(\frac{3}{7}\)
(472-168:4+755:5) x (21-3 x7) = (472-168:4+755:5) x (21 -21). = (472-168:4+755:5) x 0 = 0
vì vế trái có tính ra số nào thí nó nhân với 0 thì chắc chắn bằng 0
(472 - 168:4 + 755:5) x (21 - 3x7)
= (472 - 168:4 + 755:5) x (21 - 21)
= (472 - 168:4 + 755:5) x 0
= 0