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A x 1/5 + A x 3/10 + 1/2 x A = 500
A x (1/5 + 3/10 + 1/2) = 500
A x 2/2 = 500
A = 500 : 2/2
A = 500
Hok tốt
a) \(\frac{a}{b}:\frac{2}{3}=\frac{3}{5}-\frac{1}{10}\)
\(\Rightarrow\frac{a}{b}:\frac{2}{3}=\frac{6}{10}-\frac{1}{10}\)
\(\Rightarrow\frac{a}{b}:\frac{2}{3}=\frac{5}{10}\)
\(\Rightarrow\frac{a}{b}=\frac{5}{10}x\frac{2}{3}\)
\(\Rightarrow\frac{a}{b}=\frac{10}{30}\)
\(\Rightarrow\frac{a}{b}=\frac{1}{3}\)
b, \(\frac{a}{b}x\frac{1}{5}=\frac{3}{5}+1\)
\(\Rightarrow\frac{a}{b}x\frac{1}{5}=\frac{3}{5}+\frac{5}{5}\)
\(\Rightarrow\frac{a}{b}x\frac{1}{5}=\frac{8}{5}\)
\(\Rightarrow\frac{a}{b}=\frac{8}{5}:\frac{1}{5}\)
\(\Rightarrow\frac{a}{b}=\frac{8}{5}x5\)
\(\Rightarrow\frac{a}{b}=8\)
4/5 + ( x : 2/3 - 1/3 ) = 9/10
( x: 2/3 - 1/3 ) = 9/10 - 4/5
x : 2/3 - 1/3 = 1/10
x : 2/3 = 1/10 + 1/3
x : 2/3 = 13/30
x = 13/30 . 2/3
x =13/45
Bài 1:
a) \(x.\dfrac{3}{4}=\dfrac{9}{14}\)
\(\Rightarrow x=\dfrac{9}{14}:\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{6}{7}\)
b) \(x:\dfrac{5}{9}=\dfrac{3}{10}\)
\(\Rightarrow x=\dfrac{3}{10}.\dfrac{5}{9}\)
\(\Rightarrow x=\dfrac{1}{6}\)
a+a+a+a+a+a+a+a+a+a+1+2+3+4+5+6+7+8+9+10
=a x 10 +55
=a0 + 55
= a5 + 50
\(\frac{4}{5}-\frac{1}{a}=\frac{3}{10}\)
\(\frac{1}{a}=\frac{4}{5}-\frac{3}{10}\)
\(\frac{1}{a}=\frac{5}{10}\)
\(\frac{1}{a}=\frac{1}{2}\)
\(=>a=2\)
HT
\(\frac{4}{5}-\frac{1}{a}=\frac{3}{10}\)
\(\frac{1}{a}=\frac{4}{5}-\frac{3}{10}\)
\(\frac{1}{a}=\frac{1}{2}\)
\(\Rightarrow a=2\)
Câu 1: Tính nhanh:
a) ( \({4\over 5}\) + \({3\over 10}\) + \({1\over 5}\) + \({7\over 10}\) ) * 3 : \({6\over 5}\)
= ( \({4*2\over 5*2}\) + \({3\over 10}\) + \({1*2\over 5*2}\) + \({7\over 10}\) ) *3 : \({6\over 5}\)
= ( \({8\over 10}\) + \({3\over 10}\) + \({2\over 10}\) + \({7\over 10}\) ) * 3 : \({6\over 5}\)
= 2 *3 : \({6\over 5}\)
= 6 * \({5 \over 6}\)
= \({30\over 6}\) = 5
b) ( 1 + 3 + 5 + ................. + 99) * ( \({2\over 5}\) * 5 - \({1\over 2}\)*4 )
= ( 1 + 3 + 5 + ................. + 99) * ( \({2*5\over 5}\) - \({1*4\over 2}\) )
= ( 1 + 3 + 5 + ................. + 99) * ( \({10\over 5}\) - \({4\over 2}\))
= ( 1 + 3 + 5 + ................. + 99) * ( 2 - 2 )
= ( 1 + 3 + 5 + ................. + 99) * 0
= 0
3/2950