Tính bằng cách thuận tiện :
12/23 x 9/28 + 11/23 x 9/28 3 + 1/9 + 3/9 + 2 + 5/9 + 3 + 2
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Câu 1:\(\frac{12}{23}\times\frac{9}{28}+\frac{11}{23}\times\frac{9}{28}\)
\(=\frac{9}{28}\times\left(\frac{12}{23}+\frac{11}{23}\right)\)
\(=\frac{9}{28}\times\frac{23}{23}\)
\(=\frac{9}{28}\times1\)
\(=\frac{9}{28}\)
Câu 2:
\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2\)
\(=\left(3+2+2+3\right)+\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)\)
\(=10+\frac{9}{9}\)
\(=10+1\)
\(=11\)
\(\frac{12}{23}x\frac{9}{28}+\frac{11}{23}x\frac{9}{28}=\)\(\left(\frac{12}{23}+\frac{11}{23}\right)x\frac{9}{28}\)\(=\) \(1x\frac{9}{28}=\frac{9}{28}\)
\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2\)\(=\) \(\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)+\left(3+2+3+2\right)\)\(=\) \(1+3+2+3+2=\)\(11\)
a: \(=\dfrac{21}{11}+\dfrac{12}{11}+\left(-\dfrac{9}{19}-\dfrac{3}{19}-\dfrac{6}{19}\right)=3-\dfrac{18}{19}=\dfrac{39}{19}\)
b: \(=\dfrac{2}{3}+\dfrac{4}{3}+\dfrac{3}{4}+\dfrac{7}{4}+\dfrac{4}{5}+\dfrac{16}{5}=2+4+\dfrac{5}{2}=6+\dfrac{5}{2}=\dfrac{17}{2}\)
TL:
8/15 x 5/6 = 40/90 = 4/9
41/20 x 3/4 = 123/80
(11/23 + 9/23) + (18/23 + 2/23) = 20/23 + 20/23 = 40/43
HT
\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\) = \(\frac{2}{3}\times\frac{4}{5}\times\frac{5}{6}\)=\(\frac{2\times4\times5}{3\times5\times6}\)=\(\frac{2\times4\times5}{3\times5\times2\times3}\)=\(\frac{4}{9}\)
\(\frac{11}{23}+\frac{2}{23}+\frac{9}{23}+\frac{18}{23}\)=\(\frac{\left(11+9\right)+\left(18+2\right)}{23}\)=\(\frac{20+20}{23}\)=\(\frac{40}{23}\)
\(\frac{27}{12}+\frac{17}{6}-\frac{25}{36}-\frac{15}{6}\)=\(\left(\frac{27}{12}-\frac{25}{36}\right)+\left(\frac{17}{6}-\frac{15}{6}\right)\)=\(\frac{14}{9}+\frac{2}{6}\)=\(\frac{17}{9}\)
/HT\
\(1,\frac{2}{3}+\frac{4}{9}+\frac{1}{5}+\frac{2}{15}+\frac{3}{2}-\frac{17}{18}\)
\(< =>\frac{4}{9}+\frac{3}{2}+\left(\frac{2}{3}+\frac{1}{5}+\frac{2}{15}\right)-\frac{17}{18}\)
\(< =>\frac{8}{18}+\frac{27}{18}+\left(\frac{10}{15}+\frac{3}{15}+\frac{2}{15}\right)-\frac{17}{18}\)
\(< =>\frac{35}{18}+1-\frac{17}{18}\)
\(< =>\frac{53}{18}-\frac{17}{18}\)
\(< =>2\)
\(2,\frac{13}{28}\cdot\frac{5}{12}-\frac{5}{28}\cdot\frac{1}{12}\)
\(< =>\left(\frac{13}{28}-\frac{5}{28}\right)\cdot\left(\frac{5}{12}-\frac{1}{12}\right)\)
\(< =>\frac{2}{7}\cdot\frac{1}{3}\)
\(< =>\frac{2}{21}\)
\(3,\frac{19}{4}\cdot\frac{15}{23}-\frac{15}{4}\cdot\frac{7}{23}+\frac{15}{4}\cdot\frac{11}{23}\)
\(< =>\frac{285}{92}-\frac{105}{92}+\frac{165}{92}\)
\(< =>\frac{15}{4}\)
Bạn tự làm bài nếu bạn không tính được thì bạn hỏi cô hay thầy đấy nha bạn,chúc bạn học giỏi nha:
a, \(\frac{39}{19}\)
b, \(8.5\)hay \(\frac{17}{2}\)
c, \(\frac{1277}{4186}\)
Bấm máy tính là được ^_^
\(.\)
9/5 + 4/7 + 6/5 + 3/7
= ( 9/5 + 6/5 ) + ( 4/7 + 3/7)
= 3 + 1
= 4
9/5 + 4/7 + 6/5 + 3/7 = (9/5 + 6/5) + (4/7 + 3/7)
= 15/5 + 7/7
= 3 + 1
= 4
1/2 x 45/33 x 1/9 x 11/6 = (1/2 x 1/9) x (45/33 x 11/6)
= 1/18 x 45/18
= 5/2
a,17/23 + (1 - 17/23)
= 17/23 + 6/23
= 23/23 = 1
b,17/12 + 9/7 - (2/7 + 5 /12)
= (17/12 - 5/12) + (9/7 + 2/7)
= 1+1 = 2
c, 7/13 - ( 4/7 -6/13 )
= 7/13 - 4/7+ 6/13
= (7/13 + 6/13) -4/7
= 13/13 -4/7
= 1 -4/7 = 3/7
hok tốt✍️ ✍️
a) 17/23+(1-17/23)
=17/23+1-17/23
=1
b)17/12+9/7-(2/7+5/12)
=17/12+9/7-2/7-5/12
=1+1
=2
c)
7/13-(4/7-6/13)
=7/13-4/7+6/13
=1-4/7
=3/7
12/23 x 9/28 + 11/12 x 9/28
= ( 12/23 + 11/23 ) x 9/28
= 1 x 9/28 = 9/28
3 + 1/9 + 3/9 + 2 + 5/9 + 3 + 2
= ( 3 + 2 + 3 + 2 ) + ( 1/9 + 3/9 + 5/9 )
= 10 + 1
= 11