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25-2 : (3/5-1/2) + (5/2 +1/5 * 1/4 )
= 25 - 2 : 1/10 + (5/2 + 1/20)
= 25 - 20 + 51/20
= 5 + 51/20
= \(5\frac{51}{20}\)
( 3/10+ 4/5 *1/2 ) : (17/9 -4/3 : 3)
= (3/10 + 2/5) : (17/9 - 4/9)
= (-1/10) : 13/9
= -9/130
`@` `\text {Ans}`
`\downarrow`
`1/3+6/9+4/5+5/25`
`= 1/3+2/3+4/5+1/5`
`= 1+1`
`= 2`
`4/7*2/5+4/7*3/5-1/7`
`= 4/7*(2/5+3/5)-1/7`
`= 4/7*1-1/7`
`= 4/7-1/7=3/7`
.....................................................
a) 1+2+3+...+2018
=[(2018-1):1+1].(2018+1):2
=2018.2019:2
=2037171
b) 4+7+10+13+...+2017
=[(2017-4):3+1].(2017+4):2
=672.2021:2
=679056
c) 1+2-3-4+5+6-7-8+9+10-11-12+13+14
=(1+2-3-4)+(5+6-7-8)+(9+10-11-12)+13+14
=-4+(-4)+(-4)+13+14
=-12+27
=15
d) 23 x 75 + 25 x 23 + 180
=23 x (75+25) +180
=23 x 100 +180
=2300+180
2480
chúc ban hoc tốt nha
a) Số số hạng: ( 2018 - 1 ) : 1 + 1 = 2018
Tổng: 2018 x ( 2018 + 1 ) : 2 = 2 037 171
a) 3 2/7 - 2/5 + 5/7 - 3/5
= 3 + 2/7 - (2/5 + 3/5) + 5/7
= 3 + (2/7 + 5/7) - 1
= 3 + 1 - 1
= 3
b) 5 4/7 - 4/9 + 1 3/7 - 5/9
= 5 + 4/7 - 4/9 + 1 + 3/7 - 5/9
= (5 + 1) + (4/7 + 3/7) - (4/9 + 5/9)
= 6 + 1 - 1
= 6
a) \(3\dfrac{2}{7}-\dfrac{2}{5}+\dfrac{5}{7}-\dfrac{3}{5}\)
\(=\left(\dfrac{23}{7}+\dfrac{5}{7}\right)-\left(\dfrac{2}{5}+\dfrac{3}{5}\right)\)
\(=4-1\)
\(=3\)
b) \(5\dfrac{4}{7}-\dfrac{4}{9}+1\dfrac{3}{7}-\dfrac{5}{9}\)
\(=\left(\dfrac{32}{7}+\dfrac{10}{7}\right)-\left(\dfrac{4}{9}+\dfrac{5}{9}\right)\)
\(=6-1\)
\(=5\)
c \(\dfrac{2}{3}\times\dfrac{13}{4}\times\dfrac{3}{2}\times\dfrac{7}{3}\times\dfrac{4}{7}\)
= \(\dfrac{2\times13\times3\times7\times4}{3\times4\times2\times3\times7}\)
= \(\dfrac{13}{3}\)
\(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+\dfrac{1}{4.5}\)
=\(\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}\)
=\(\dfrac{1}{1}-\dfrac{1}{5}\)
=\(\dfrac{4}{5}\)
a, (\(\dfrac{41}{25}\) + \(\dfrac{17}{100}\)) + \(\dfrac{39}{25}\)
= (\(\dfrac{41}{25}\) + \(\dfrac{39}{25}\)) + \(\dfrac{17}{100}\)
= \(\dfrac{80}{25}\) + \(\dfrac{17}{100}\)
= \(\dfrac{320}{100}\) + \(\dfrac{17}{100}\)
= \(\dfrac{337}{100}\)
g, \(\dfrac{1}{12}\) + \(\dfrac{1}{20}\) + \(\dfrac{1}{30}\) + \(\dfrac{1}{42}\)
= \(\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)
= \(\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)
= \(\dfrac{1}{3}-\dfrac{1}{7}\)
= \(\dfrac{7}{21}-\dfrac{3}{21}\)
= \(\dfrac{4}{21}\)
a; 5\(\dfrac{3}{4}\) : 3 + 2\(\dfrac{1}{4}\).\(\dfrac{1}{3}\) - \(\dfrac{3}{8}\)
= \(\dfrac{23}{4}\) : 3 + \(\dfrac{9}{4}\).\(\dfrac{1}{3}\) - \(\dfrac{3}{8}\)
= \(\dfrac{23}{4}\) x \(\dfrac{1}{3}\) + \(\dfrac{3}{4}\) - \(\dfrac{3}{8}\)
= \(\dfrac{23}{12}\) + \(\dfrac{3}{4}\) - \(\dfrac{3}{8}\)
= \(\dfrac{46}{24}\) + \(\dfrac{18}{24}\) - \(\dfrac{9}{24}\)
= \(\dfrac{64}{24}\) - \(\dfrac{9}{24}\)
= \(\dfrac{55}{24}\)
(dấu . là dấu nhân )
a, \(\frac{3}{2}\cdot\frac{4}{7}+\frac{3}{7}\cdot\frac{3}{2}\)
= \(\frac{3}{2}\left(\frac{4}{7}+\frac{3}{7}\right)\)
=\(\frac{3}{2}\cdot\frac{7}{7}=\frac{3}{2}\)
b, \(\frac{12}{5}\cdot4-4\cdot\frac{7}{5}\)
=\(4\left(\frac{12}{5}-\frac{7}{5}\right)=4\cdot\frac{5}{5}=4\)
c, \(\frac{5}{11}:\frac{1}{2}+\frac{6}{11}:\frac{1}{2}\)
=\(2\left(\frac{5}{11}+\frac{6}{11}\right)=2\cdot\frac{11}{11}=2\)
a;3/2x(4/7+3/7)
=3/2x1
=3/2
b;12/5x4-4x7/5
=4x(12/5-7/5)
=4x1
=4
c;5/11:1/2+6/11:1/2
=1/2:(5/11+6/11)
=1/2:1
=1/2
\(\frac{9}{2}\) \(-\) ( \(x\) \(-\) \(\frac{3}{4}\) ) = \(\frac{25}{4}\)
\(x\) \(-\) \(\frac{3}{4}\) = \(\frac{9}{2}\) \(-\) \(\frac{25}{4}\)
\(x\) \(-\) \(\frac{3}{4}\) = \(-\frac{7}{4}\)
\(x\) = \(-\frac{7}{4}\) \(+\) \(\frac{3}{4}\)
\(x\) = \(-1\)
\(4\) \(+\) \(x\) \(+\) \(\frac{3}{4}\) = \(\frac{17}{2}\)
( \(4\) \(+\) \(\frac{3}{4}\)) \(+\)\(x\) = \(\frac{17}{2}\)
\(\frac{19}{4}\) \(+\) \(x\) = \(\frac{17}{2}\)
\(x\) = \(\frac{17}{2}\) \(-\) \(\frac{19}{4}\)
\(x\) = \(\frac{15}{4}\)
A) 2 và 1/3 ÷7/9+2/5× 1 và 2/3 -7/3
= 7/3 : 7/9 + 2/5 x 5/3 - 7/3
= 7/3 x 9/7 + 2/5 x 5/3 - 7/3
= 7/3 x ( 9/7 + 2/5 x 5/3 )
= 7/3 x ( 9/7 + 2/3 )
= 7/3 x 41/21= 41/9
B) 25% ×4/5 +3/5 -0.8 +2010
= (1/4 ×4/5 ) + ( 3/5 - 4/5 ) +2010
= 1/5 + -1/5 + 2010
= 0 + 2010
= 2010