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\(\dfrac{12}{6.7}+\dfrac{12}{7.22}+\dfrac{12}{22.15}+\dfrac{12}{15.38}+...+\dfrac{12}{97.202}\)
\(=12.\left(\dfrac{1}{6.7}+\dfrac{1}{7.22}+\dfrac{1}{22.15}+\dfrac{1}{15.38}...+\dfrac{1}{97.202}\right)\)
\(=12.\left(\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{22}+\dfrac{1}{22}-\dfrac{1}{15}+...+\dfrac{1}{97}-\dfrac{1}{202}\right)\)
\(=12.\left(\dfrac{1}{6}-\dfrac{1}{202}\right)\)
\(=\dfrac{196}{101}\)
\(D=12\cdot\left(\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{22}+...+\frac{1}{97}-\frac{1}{202}\right)\)
\(D=12\cdot\left(\frac{1}{6}-\frac{1}{202}\right)\)
\(D=12\cdot\frac{49}{303}\)
\(D=\frac{588}{303}\)
a) 9 . 24 . 25
= 9 . 600
= 5400
b) 12 . 125 . 5 = (12 . 5) . 125
= 60 . 125 =7500
c) 64 . 125 . 875= 8000 . 875 = 7000000
d) 425 . 7 . 4 - 170 . 60 = 1700 . 7 - 170 . 60
= 170 . (10 . 7) - 170 . 60
= 170 . 70 - 170 . 60
= 170 . (70 - 60)
= 170 . 10 = 1700
\(-\frac{4}{12}+\frac{18}{45}-\frac{6}{9}-\frac{21}{35}+\frac{6}{30}\)
\(=\frac{-1}{3}+\frac{2}{5}-\frac{1}{3}-\frac{3}{5}+\frac{1}{5}\)
\(=0\)
\(\frac{6.4+6.7}{6.5+12}=\frac{4+1.7}{1.5+2}=\frac{4+7}{5+2}=\frac{11}{7}\)
\(\frac{6\cdot4+6\cdot7}{6\cdot5+12}\)
\(=\frac{6\left(4+7\right)}{6\cdot5+6\cdot2}\)
\(=\frac{6\left(4+7\right)}{6\left(5+2\right)}\)
\(=\frac{11}{7}\)
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