Question

Answer 1

e, \(\dfrac{11}{19}+\dfrac{19}{18}+\dfrac{8}{19}-\dfrac{1}{18}+5.2\)
\(=\left(\dfrac{11}{19}+\dfrac{8}{19}\right)+\left(\dfrac{19}{18}-\dfrac{1}{18}\right)+10\)
\(=\dfrac{19}{19}+\dfrac{18}{18}+10\)
\(=1+1+10\)
\(=2+10\)
\(=20\)
f, \(\dfrac{3}{7}.\dfrac{16}{15}-\dfrac{3}{7}.\dfrac{2}{15}\)
\(=\dfrac{3}{7}.\left(\dfrac{16}{15}-\dfrac{2}{15}\right)\)
\(=\dfrac{3}{7}.\dfrac{14}{15}\)
\(=\dfrac{1.2}{1.5}\)
\(=\dfrac{2}{5}\)
g, \(\dfrac{15}{37}+\dfrac{17}{53}+\dfrac{22}{37}-\dfrac{70}{53}\)
\(=\left(\dfrac{15}{37}+\dfrac{22}{37}\right)+\left(\dfrac{17}{53}-\dfrac{70}{53}\right)\)
\(=\dfrac{37}{37}-\dfrac{-53}{53}\)
\(=1+\left(-1\right)\)
\(=0\)
h,\(\left(\dfrac{2}{9}-\dfrac{7}{12}\right):\dfrac{3}{4}+\left(\dfrac{16}{9}-\dfrac{5}{12}\right):\dfrac{3}{4}\)
\(=\left(\dfrac{8}{36}-\dfrac{21}{36}\right).\dfrac{4}{3}+\left(\dfrac{64}{36}-\dfrac{15}{36}\right).\dfrac{4}{3}\)
\(=\dfrac{-13}{36}.\dfrac{4}{3}+\dfrac{49}{36}.\dfrac{4}{3}\)
\(=\dfrac{4}{3}.\left(\dfrac{-13}{36}+\dfrac{49}{36}\right)\)
\(=\dfrac{4}{3}.\dfrac{36}{36}\)
\(=\dfrac{4}{3}.1\)
\(=\dfrac{4}{3}\)

Answer 2

Bài 4:
\(a,\dfrac{15}{34}+\dfrac{-7}{27}+\dfrac{19}{34}-\dfrac{20}{27}+\dfrac{21}{7}\)
\(=\left(\dfrac{15}{34}+\dfrac{19}{34}\right)+\left(\dfrac{-7}{27}-\dfrac{20}{27}\right)+\dfrac{21}{7}\)
\(=\dfrac{34}{34}+\dfrac{-27}{27}+3\)
\(=1+\left(-1\right)+3\)
\(=0+3\)
\(=3\)
\(b,\dfrac{-3}{5}+0,8.\left(-7\dfrac{1}{2}\right)\)
\(=\dfrac{-3}{5}+\dfrac{4}{5}.\dfrac{-15}{2}\)
\(=\dfrac{-3}{5}.\dfrac{2.\left(-3\right)}{1}\)
\(=\dfrac{-3}{5}.\left(-6\right)\)
\(=\dfrac{18}{5}\)
\(c,-\dfrac{1}{4}.13\dfrac{9}{11}-0,25.6\dfrac{2}{11}\)
\(=-\dfrac{1}{4}.13\dfrac{9}{11}-\dfrac{1}{4}.6\dfrac{2}{11}\)
\(=-\dfrac{1}{4}.\left(13\dfrac{9}{11}+6\dfrac{2}{11}\right)\)
\(=-\dfrac{1}{4}.\left(\dfrac{152}{11}+\dfrac{68}{11}\right)\)
\(=-\dfrac{1}{4}.\dfrac{220}{11}\)
\(=\dfrac{-1}{4}.20\)
\(=\dfrac{\left(-1\right).5}{1}\)
\(=-5\)
\(d,\dfrac{4}{9}:\left(-\dfrac{1}{7}\right)+6\dfrac{5}{9}:\left(-\dfrac{1}{7}\right)\)
\(=\dfrac{4}{9}.\left(-7\right)+\dfrac{59}{9}:\left(-\dfrac{1}{7}\right)\)
\(=\dfrac{4}{9}.\left(-7\right)+\dfrac{59}{9}.\left(-7\right)\)
\(=\left(-7\right).\left(\dfrac{4}{9}+\dfrac{59}{9}\right)\)
\(=\left(-7\right).\dfrac{63}{9}\)
\(=\left(-7\right).7\)
\(=-49\)