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\(\dfrac{2}{5}\) x 5 + 4 x \(\dfrac{2}{5}\) + \(\dfrac{2}{5}\)
= \(\dfrac{2}{5}\) x (5 + 4 + 1)
= \(\dfrac{2}{5}\) x 10 = 4
(1 - \(\dfrac{1}{2}\) ) x (1 - \(\dfrac{3}{5}\) ) x (1 - \(\dfrac{2}{7}\) ) x (1 - \(\dfrac{2}{9}\) )
= \(\dfrac{1}{2}\) x \(\dfrac{2}{5}\) x \(\dfrac{5}{7}\) x \(\dfrac{7}{9}\)
= \(\dfrac{1}{9}\)
Bài 1:
a: Cách 1: \(\left(\frac23-\frac45\right)\times25\)
\(=\left(\frac{10}{15}-\frac{12}{25}\right)\times25\)
\(=-\frac{2}{25}\times15=-\frac{30}{15}=-\frac65\)
Cách 2: \(\left(\frac23-\frac45\right)\times25\)
\(=\frac23\times25-\frac45\times25\)
\(=\frac{50}{3}-20=\frac{50}{3}-\frac{100}{5}=\frac{50}{3}-20=\frac{50}{3}-\frac{60}{3}=-\frac{10}{3}\)
b: Sửa đề: \(\frac34\times\frac25+\frac34\times\frac27\)
Cách 1: \(\frac34\times\frac25+\frac34\times\frac27\)
\(=\frac34\times\left(\frac25+\frac27\right)\)
\(=\frac34\times\left(\frac{14}{35}+\frac{10}{35}\right)\)
\(=\frac34\times\frac{24}{35}=\frac{72}{140}=\frac{18}{35}\)
Cách 2:
\(\frac34\times\frac25+\frac34\times\frac27\)
\(=\frac{6}{20}+\frac{6}{28}\)
\(=\frac{42}{140}+\frac{30}{140}=\frac{72}{140}=\frac{18}{35}\)
Bài 2:
a: \(x:\frac25=\frac23\)
=>\(x=\frac23\times\frac25=\frac{4}{15}\)
b: \(x:\frac23=\frac49\)
=>\(x=\frac49\times\frac23=\frac{8}{27}\)
\(a.\dfrac{3\times4\times7}{12\times8\times9}=\dfrac{3\times4\times7}{3\times4\times4\times2\times9}\\ =\dfrac{7}{4\times2\times9}=\dfrac{7}{72}\\ b.\dfrac{4\times5\times6}{12\times10\times8}=\dfrac{4\times5\times2\times3}{4\times3\times5\times2\times4\times2}=\dfrac{1}{8}\\ c.\dfrac{5\times6\times7}{12\times14\times15}=\dfrac{5\times6\times7}{2\times6\times7\times2\times5\times3}\\ =\dfrac{1}{2\times2\times3}=\dfrac{1}{12}\)
a) [ {4/5+1/5+3/10 } +1/7 ] * [3 : 6/5 ] = 13/10 * 5/2 = 13/4
b) = [1+3+5+...99] x [ 2/5 x5 - 1/2 *4 ]=[(99+1)+(98+2)+(97+3) +...+(49+51)] x 0 = 0
a) \(\frac{1}{3}+\frac{1}{4}-\frac{1}{5}\)
\(=\frac{23}{60}\)
b) \(\frac{5}{2}+\frac{1}{3}-\frac{1}{4}\)
\(=\frac{31}{12}\)
c) \(\frac{10}{3}-\left(\frac{1}{4}+\frac{1}{12}\right)\)
\(=\frac{9}{3}=3\)
d) \(\frac{1}{3}+\frac{6}{5}-\frac{1}{15}\)
\(=\frac{22}{15}\)
trả lòi:
A)= 23/60
B)= 31/12
C)= 3* vì 3/9 cùng chia hết cho 3*
D)= 22/15
Hc tốt!
1) 1/3 x 1/2 x 3/7 = 1/6 x 3/7 = 1/14
2) 5/4 x 1/3 + 1/7 = 5/12 + 1/7 = 47/84
3) 8 x (8/9 - 2/3) = 8 x 2/9 = 16/9
4) 5/6 x 48/20 x 1/2 = 2 x 1/2 = 1
5) (2/5 + 3/4) x 8 = 23/20 x 8 = 46/5
6) 10 x (1/2 - 1/5) = 10 x 3/10 = 3
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