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Bài 1.
a) 1 gấp bao nhiêu lần \( \frac{1}{10}\) ?
b) \( \frac{1}{10}\) gấp bao nhiêu lần \( \frac{1}{100}\) ?
c) \( \frac{1}{100}\) gấp bao nhiêu lần \( \frac{1}{1000}\) ?
a) \(1\) gấp \(10\) lần \( \frac{1}{10}\) ;
b) \( \frac{1}{10}\) gấp \(10\) lần \( \frac{1}{100}\) ;
c) \( \frac{1}{100}\) gấp \(10\) lần \( \frac{1}{1000}\) ;
Bài 2. Tìm \(x\):
a) \(x + \frac{2}{5}\) = \( \frac{1}{2}\) ; b) \(x – \frac{2}{5}\) = \( \frac{2}{7}\) ;
c) \(x\times\frac{3}{4}\) = \( \frac{9}{20}\) ; d) \(x : \frac{1}{7}\) = 14.
Giải
Advertisements (Quảng cáo)
a) \(x + \frac{2}{5}\) = \( \frac{1}{2}\) b) \(x – \frac{2}{5}\) = \( \frac{2}{7}\)
\(x = \frac{1}{2}\) – \( \frac{2}{5}\) \(x = \frac{2}{7}\) + \( \frac{2}{5}\)
\(x ={5 \over {10}} – {4 \over {10}}\) \(x={{10} \over {35}} + {{14} \over {35}}\)
\(x= \frac{1}{10}\) \(x = \frac{24}{35}\)
c) \(x \times \frac{3}{4}\) = \( \frac{9}{20}\) d) \(x :\frac{1}{7}= 14\)
\(x = \frac{9}{20}\) : \( \frac{3}{4}\) \(x = 14 \times\frac{1}{7}\)
\(x = {9 \over {20}} \times {4 \over 3}\) \(x = {{14 \times 1} \over 7} = {{7 \times 2} \over 7}\) \(x = 2\).
\(x = {{9 \times 4} \over {20 \times 3}} = {{3 \times 3 \times 4} \over {5 \times 4 \times 3}}\)
\(x =\frac{3}{5}\)