Question

2. thực hiện phép tính

a. \(\dfrac{3}{4}\)+\(\dfrac{3}{5}\)-\(\dfrac{18}{60}\)

b. \(\dfrac{17}{8}\)-\(\dfrac{11}{6}\)-\(\dfrac{2}{9}\)

c. \(\dfrac{20}{45}\)+\(\dfrac{14}{35}\)+\(\dfrac{32}{44}\)

d.\(\dfrac{23}{29}\)+\(\dfrac{5}{11}\)+\(\dfrac{17}{11}\)

e.\(17\dfrac{25}{27}\)+\(3\dfrac{7}{2}\)

Answer 1

a) \(\dfrac{3}{4}+\dfrac{3}{5}-\dfrac{18}{60}\) ( MTC: 60)

= \(\dfrac{3.15}{4.15}+\dfrac{3.12}{5.12}-\dfrac{18}{60}\)

= \(\dfrac{45}{60}+\dfrac{36}{60}-\dfrac{18}{60}\)

= \(\dfrac{45+36-18}{60}\)=\(\dfrac{63}{60}=\dfrac{21}{20}\)

b)\(\dfrac{17}{8}-\dfrac{11}{6}-\dfrac{2}{9}\) (MTC:72)

=\(\dfrac{17.9}{8.9}-\dfrac{11.12}{6.12}-\dfrac{2.8}{9.8}\)

= \(\dfrac{153}{72}-\dfrac{132}{72}-\dfrac{16}{72}\)

=\(\dfrac{153-132-16}{72}\)

=\(\dfrac{5}{72}\)

c)\(\dfrac{23}{29}+\dfrac{5}{11}+\dfrac{17}{11}\) (MTC:319)

= \(\dfrac{23.11}{29.11}+\dfrac{5.29}{11.29}+\dfrac{17.29}{11.29}\)

=\(\dfrac{253}{319}+\dfrac{145}{319}+\dfrac{493}{319}\)

=\(\dfrac{253+145+493}{319}\)=\(\dfrac{891}{319}=\dfrac{81}{29}\)

Answer 2

c) \(\dfrac{20}{45}+\dfrac{14}{35}+\dfrac{32}{44}\)

= \(\dfrac{4}{9}+\dfrac{2}{5}+\dfrac{8}{11}\)(Rút gọn b/thức)(MTC:495)

=\(\dfrac{4.55}{9.55}+\dfrac{2.99}{5.99}+\dfrac{8.45}{11.45}\)

=\(\dfrac{220}{495}+\dfrac{198}{495}+\dfrac{360}{495}\)

=\(\dfrac{220+198+360}{495}\)=\(\dfrac{778}{495}\)

e)\(17\dfrac{25}{27}+3\dfrac{7}{2}\)

= \(\dfrac{484}{27}+\dfrac{13}{2}\) (MTC:54)

=\(\dfrac{484.2}{27.2}+\dfrac{13.27}{2.27}\)

\(=\dfrac{968}{54}+\dfrac{351}{54}\)

=\(\dfrac{968+351}{54}=\dfrac{1319}{54}\)