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5/9x12/7=20/21
6/5:8/3=9/20
9/20x5/12=3/16
15/16:25/24=9/10
14x5/21=10/3
10:5/3=6
5/3:10=1/6
5/9 x 12/7 = 60/63
6/5 : 8/3 = 6/5 x 3/8 = 9/20
9/20 x 5/12 = 3/16
15/16 : 25/24 = 15/16 x 24/25 = 9/10
14 x 5/21 = 60/21
10 : 5/3 = 10 x 3/5 = 6
5/3 : 10 = 5/3 x 1/10 = 1/6

a) 1/2x(3/4+2/5)
1/2x23/20
23/40
b) 3/4:(8/9+16/3)
3/4:56/9
27/224
c) 1/5:1/10-1/3
2-1/3
5/3
d) 3/4x(20/9-8/15)
3/4x76/45
19/15
e) 1/7:5/14-3/2
=2/5-3/2
-11/10 ( Chị nghĩ lớp 4 chưa học đến số âm nên em xem lại đề nhé)
g) 3/2x(11/6-5/12)
3/2x17/12
17/8
a)\(\frac{1}{2}x\left(\frac{3}{4}+\frac{2}{5}\right)\)
\(=\frac{1}{2}x\left(\frac{15}{20}+\frac{8}{20}\right)\)
\(=\frac{1}{2}x\frac{23}{20}\)
\(=\frac{23}{40}\)
b)\(\frac{3}{4}:\left(\frac{8}{9}+\frac{16}{3}\right)\)
\(=\frac{3}{4}:\left(\frac{8}{9}+\frac{48}{9}\right)\)
\(=\frac{3}{4}:\frac{56}{9}\)
\(=\frac{3}{4}x\frac{9}{56}\)
\(=\frac{27}{224}\)
c) \(\frac{1}{5}:\frac{1}{10}-\frac{1}{3}\)
\(=\frac{1}{5}x10-\frac{1}{3}\)
\(=2-\frac{1}{3}\)
\(=\frac{6}{3}-\frac{1}{3}=\frac{5}{3}\)
d) \(\frac{3}{4}x\left(\frac{20}{9}-\frac{8}{15}\right)\)
\(=\frac{3}{4}x\left(\frac{100}{45}-\frac{24}{45}\right)\)
\(=\frac{3}{4}x\frac{76}{45}\)
\(=\frac{19}{5}\)
e) \(\frac{1}{7}:\frac{5}{14}-\frac{3}{2}\)
\(=\frac{1}{7}x\frac{14}{5}-\frac{3}{2}\)
\(=\frac{2}{5}-\frac{3}{2}\)
\(=\frac{4}{10}-\frac{15}{10}\)
\(=\frac{-11}{10}\)
g) \(\frac{3}{2}x\left(\frac{11}{6}-\frac{5}{12}\right)\)
\(=\frac{3}{2}x\left(\frac{22}{12}-\frac{5}{12}\right)\)
\(=\frac{3}{2}x\frac{17}{12}\)
=\(=\frac{17}{8}\)

(15x1-15) x) (10+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20)
= (15-15) x (10+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20)
= 0 x (10+1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20)
= 0
= (15 - 15)\(\times\)(10 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +12 +13 +14 +15 +16 +17 +18 +19 +20)
= 0\(\times\)(10 +1 +2 +3 +4 +5 +6 +7 +8 +9 +10 +11 +12 +13 +14 +15 +16 +17 +18 +19 +20)
= 0

TL
\(\frac{3}{5}=\frac{3x2}{5x2}=\frac{6}{10}\) (cách làm là nhan cả tử và mẫu với một số )
tương tự
\(\frac{3}{5}=\frac{6}{10}=\frac{9}{15}=\frac{12}{20}\)
HT

\(\dfrac{9}{10}+\dfrac{3}{5}\times\dfrac{1}{6}=\dfrac{9}{10}+\dfrac{3}{30}=\dfrac{27}{30}+\dfrac{3}{30}=1\)
\(\dfrac{31}{12}-\dfrac{7}{5}:\dfrac{14}{15}=\dfrac{31}{12}-\dfrac{7}{5}\times\dfrac{15}{14}=\dfrac{31}{12}-\dfrac{3}{2}=\dfrac{31}{12}-\dfrac{18}{12}=\dfrac{13}{12}\)
\(\dfrac{4}{7}\times\dfrac{2}{5}:\dfrac{10}{9}=\dfrac{14}{35}\times\dfrac{9}{10}=\dfrac{9}{25}\)

\(\frac{50}{150}=\frac{1}{3}\)
\(\frac{5}{20}=\frac{1}{4}\)
\(\frac{8}{32}=\frac{1}{4}\)
Sau đó bạn cứ rút gọn thôi,tích cho tớ nha
- \(\frac{1}{3}\)
- \(\frac{1}{4}\)
- \(\frac{1}{4}\)
- \(\frac{2}{3}\)
- \(\frac{2}{3}\)
- \(\frac{3}{2}\)
- \(\frac{3}{5}\)
- \(\frac{1}{2}\)
- \(\frac{18}{5}\)
- \(\frac{1}{4}\)
- \(\frac{1}{25}\)
- \(\frac{1}{8}\)
- \(\frac{1}{2}\)
- \(\frac{3}{7}\)
- \(\frac{2}{3}\)
- \(\frac{1}{3}\)
- k cho mk nha

\(x+\frac{10}{4}x\frac{2}{5}:\frac{12}{9}=\frac{15}{20} \)
\(x+1=\frac{15}{20}x\frac{12}{9}\)
\(x+1=1\)
\(x=1-1\)
\(x=0\)
Học Tốt!~!
thanks
l