Question

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tính nhanh

19/28 + 23/47 - 15/8 + 9/28 + 24/47

30/11 + 12/35 - 19/11 - 2/35 - 2/7

Answer 1

[HT.Phong (9A5)]

\(\dfrac{19}{28}+\dfrac{23}{47}-\dfrac{15}{8}+\dfrac{9}{28}+\dfrac{24}{47}\)

\(=\left(\dfrac{19}{28}+\dfrac{9}{28}\right)+\left(\dfrac{23}{47}+\dfrac{24}{47}\right)-\dfrac{15}{8}\)

\(=\dfrac{28}{28}+\dfrac{47}{47}-\dfrac{15}{8}\)

\(=1+1-\dfrac{15}{8}\)

\(=\dfrac{1}{8}\)

____________________

\(\dfrac{30}{11}+\dfrac{12}{35}-\dfrac{19}{11}-\dfrac{2}{35}-\dfrac{2}{7}\)

\(=\left(\dfrac{30}{11}-\dfrac{19}{11}\right)+\left(\dfrac{12}{35}-\dfrac{2}{35}\right)-\dfrac{2}{7}\)

\(=\dfrac{11}{11}+\dfrac{10}{35}-\dfrac{2}{7}\)

\(=1+\dfrac{2}{7}-\dfrac{2}{7}\)

\(=1\)