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68,4 - 25,7 = 42,7
54,3 + 65,4 = 119,7
69 - 7,85 = 61,15
bài 1:
\(\frac{6}{11}+\frac{1}{3}+\frac{5}{11}\)
\(=\left(\frac{6}{11}+\frac{5}{11}\right)+\frac{1}{3}\)
\(=\frac{11}{11}+\frac{1}{3}=1+\frac{1}{3}=\frac{3}{3}+\frac{1}{3}=\frac{4}{3}\)
bài 2:
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}\)
\(=\left(\frac{1}{2}+\frac{1}{20}\right)+\left(\frac{1}{6}+\frac{1}{12}\right)\)
\(=\frac{11}{20}+\frac{1}{4}=\frac{11}{20}+\frac{5}{20}=\frac{15}{20}=\frac{3}{4}\)
bài 3:
a) \(\frac{3}{2}\cdot\frac{4}{5}\cdot\frac{2}{3}=\left(\frac{3}{2}\cdot\frac{2}{3}\right)\cdot\frac{4}{5}=1\cdot\frac{4}{5}=\frac{4}{5}\)
b) \(\frac{6}{7}\cdot\frac{5}{3}\cdot\frac{7}{6}=\left(\frac{6}{7}\cdot\frac{7}{6}\right)\cdot\frac{5}{3}=1\cdot\frac{5}{3}=\frac{5}{3}\)
bài 4:
a) \(\frac{2}{5}\cdot\frac{1}{4}+\frac{3}{4}\cdot\frac{2}{5}=\frac{2}{5}\cdot\left(\frac{1}{4}+\frac{3}{4}\right)=\frac{2}{5}\cdot1=\frac{2}{5}\)
b) \(\frac{6}{11}:\frac{2}{3}+\frac{5}{11}:\frac{2}{3}=\left(\frac{6}{11}+\frac{5}{11}\right):\frac{2}{3}=1:\frac{2}{3}=\frac{3}{2}\)
Bài 1:
6/11 + 1/3 + 5/11
= ( 6/11 + 5/11) + 1/3
= 11/11 + 1/3
= 1 + 1/3
= 3/3 +1/3
= 4/3
Bài 2:
1/2 + 1/6 + 1/12 + 1/20
= ( 1/2 + 1/6 + 1/12 ) + 1/20
= ( 6/12 + 2/12 + 1/12 ) + 1/20
=9/12 + 1/20
= 3/4 +1/20
= 15/20 + 1/20
= 16/20 = 4/5
Bài 3:
a) \(\frac{3}{2}\times\frac{4}{5}\times\frac{2}{3}\) \(=\left(\frac{3}{2}\times\frac{2}{3}\right)\times\frac{4}{5}\)\(=1\times\frac{4}{5}=\frac{4}{5}\)
b) \(\frac{6}{7}\times\left(\frac{5}{3}\times\frac{7}{6}\right)\) \(=\frac{6}{7}\times\frac{35}{18}\)\(=\frac{1\times5}{7\times3}=\frac{5}{21}\)
Bài 4:
a) 2/5 x 1/4 + 3/4 x 2/5
= 2/5 x ( 1/4 + 3/4)
= 2/5 x 1
= 2/5
b) 6/11 : 2/3 +5/11 : 2/3
= ( 6/11 + 5/11) x 3/2
= 11/11 x 3/2
= 1 x 3/2
= 3/2
....
Bài 1 :
7/21 , 6/21 , 5/21
Bài 2 :
2/5 = 6/15 = 24/60
4/7 = 8/14 = 16/28
Bài 3 :
1/2 = 5/10
4/5 = 80/100
71/20 = 355/100
84/400 = 21/100
Bài 4 :
2/7 , 3/5 , 7/8 , 4/3
Câu 1:
A = (a x 7 + a x 8 - a x 15) : (1 + 2 + 3 + ........ + 10)
A = a x(7+8-15) : (1+2+3+...+10)
A = a x 0 : (1+2+3+...+10)
A = 0: (1+2+3+4+...+10)
A = 0
Câu 2:
B = (18 - 9 x 2) x (2 + 4 + 6 + 8 + 10)
B = (18 - 18) x (2+4+6+8+10)
B = 0 x ( 2 + 4 + 6 + 8 +10)
B = 0
Giáng sinh vui vẻ nhé !
A = {a x (7 + 8 - 15 ) }: (1+2+3+4+........+10)
= {a x 0 } : (1+2+3+4+........+10)
= 0 : (1+2+3+4+........+10)
= 0
đây câu A đây
a) \(\frac{11}{15}+\frac{5}{7}+\frac{2}{7}+\frac{4}{15}\)
\(=\left(\frac{11}{15}+\frac{4}{15}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)\)
\(=\frac{15}{15}+\frac{7}{7}\)
\(=1+1\)
\(=2\)
b) \(\frac{17}{10}+\frac{1}{2}-\frac{7}{10}\)
\(=\left(\frac{17}{10}-\frac{7}{10}\right)+\frac{1}{2}\)
\(=1+\frac{1}{2}\)
\(=\frac{2}{2}+\frac{1}{2}\)
\(=\frac{3}{2}\)
14×25×6×7
=350×6×7
=2100×7
=14700
125×98×2×8×25
=12250×2×8×25
=24500×8×25
=196000×25
=4900000
a, =(5+40)+(8+37)+(11+34)+(14+31)+(17+28)+(20+23)
= 45 + 45 + 45 + 45 + 45 + 43
= 90 + 90 + 83
= 180 + 83
= 263