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\(\dfrac{3}{8}+\dfrac{4}{10}=\dfrac{30}{80}+\dfrac{32}{80}=\dfrac{62}{80}=\dfrac{31}{40}\)

\(-\dfrac{3}{4}+\dfrac{5}{7}+\dfrac{7}{2}\)

\(=-\dfrac{21}{28}+\dfrac{20}{28}+\dfrac{98}{28}\)

\(=\dfrac{97}{28}\)

4% của 15 là:

\(15\times\dfrac{4}{100}=0,6\) 

\(\dfrac{12:12}{60:12}=\dfrac{1}{5}\)

\(\sqrt{27}-2\sqrt{3}+2\sqrt{48}-3\sqrt{75}\)

\(=3\sqrt{3}-2\sqrt{3}+\sqrt{192}-\sqrt{675}\)

\(=3\sqrt{3}-2\sqrt{3}+8\sqrt{3}-15\sqrt{3}\)

\(=-6\sqrt{3}\)

\(\dfrac{11}{12}=\dfrac{11\times4}{12\times4}=\dfrac{44}{48}\) và \(\dfrac{7}{48}\)

\(\dfrac{61}{200}\) và \(\dfrac{9}{50}=\dfrac{9\times4}{50\times4}=\dfrac{36}{200}\)

\(\dfrac{1}{3}=\dfrac{1\times15}{3\times15}=\dfrac{15}{45}\);\(\dfrac{2}{15}=\dfrac{2\times3}{15\times3}=\dfrac{6}{45}\) và \(\dfrac{4}{45}\)

a) 10 001

b) 9 876

c) 10 234

d) 1 023

Chọn phương án A.