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35 . 34 + 35 . 38 + 65 . 75 + 65 . 45 + 35 . 34 =
= 35 . 34 + 35 . 38 + 35 . 34 + 65 . 75 + 65 . 45
= 35 . ( 34 + 38 + 34 ) + 65 . ( 75 + 45 )
= 35 . 110 + 65 . 110
= 110 . ( 35 + 65 )
= 110 . 100
= 11000
Hok tốt!!!!!!!!!!!!!
a) Tính bằng cách hợp lí nhất :
35 . 34 + 35 . 38 + 65 . 75 + 65 . 45 + 35 . 34
= 35 . 34 + 35 . 38 + 35 . 34 + 65 . 75 + 65 . 45
= 35 . ( 34 + 38 + 34 ) + 65 . ( 75 + 45 )
= 35 . 106 + 65 . 120
= 3710 + 7800
= 11510
3 . 25 . 8 + 4 . 37 . 6 + 2 . 38 . 12
= 3 . 8 . 25 + 4 . 6 . 37 + 2 . 12 . 38
= 24 . 25 + 24 . 37 + 24 . 38
= 24 . ( 25 + 37 + 38 )
= 24 . 100
= 2400
b) Tìm số tự nhiên x, biết :
( x - 5 ) ( x + 7 ) = 0
\(\Rightarrow\orbr{\begin{cases}x-5=0\\x+7=0\end{cases}\Rightarrow\orbr{\begin{cases}x=5\\x=-7\end{cases}}}.\)
Vậy .......
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a) 4 giờ 22 phút x 4 + 5 giờ 38 phút x 4
= ( 4 giờ 22 phút + 5 giờ 38 phút ) x 4
= 10 giờ x 4
=40 giờ
b) 7 phút 30 giây x 7 - 6 phút 30 giây x 7
= ( 7 phút 30 giây - 6 phút 30 giây ) x 7
= 1 phút x 7
= 7 phút
Kết bn với mik nha!
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a) \(\frac{7}{9}\)và \(\frac{11}{13}\)
Ta có : \(1-\frac{7}{9}=\frac{2}{9};1-\frac{11}{13}=\frac{2}{13}\)
Vì \(\frac{2}{9}>\frac{2}{13}\)nên \(\frac{7}{9}< \frac{11}{13}\).
b) \(\frac{125}{121}\)và \(\frac{413}{409}\)
Ta có : \(\frac{125}{121}-1=\frac{4}{121};\frac{413}{409}-1=\frac{4}{409}\)
Vì \(\frac{4}{121}>\frac{4}{409}\)nên \(\frac{125}{121}>\frac{413}{409}\)
c) \(\frac{8}{7}\)và \(\frac{4}{5}\)
Vì \(\frac{8}{7}>1;1>\frac{4}{5}\)nên \(\frac{8}{7}>\frac{4}{5}\)
d) \(\frac{46}{35}\)và \(\frac{41}{38}\)
Chon phân số trung gian là : \(\frac{46}{38}\)
Vì \(\frac{46}{35}>\frac{46}{38};\frac{46}{38}>\frac{41}{38}\)nên \(\frac{46}{35}>\frac{41}{38}\)
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1> a) \(\frac{5}{7}x4:\frac{5}{9}=\frac{5}{7}:\frac{5}{9}x4=\frac{5}{7}x\frac{9}{5}x4=\frac{9}{7}x4=\frac{9x4}{7}=\frac{36}{7}\)
\(b,8x\frac{2}{3}:\frac{1}{2}=8x\frac{2}{3}x\frac{2}{1}=8x2x\frac{2}{3}=16x\frac{2}{3}=\frac{32}{3}\)
\(c,6:\frac{3}{5}-\frac{7}{6}x\frac{6}{7}=6x\frac{5}{3}-1=10-1=9\)
\(\frac{21}{5}x\frac{10}{11}+\frac{57}{11}=\frac{42}{11}+\frac{57}{11}=\frac{99}{11}=9\)
2) a) \(\frac{35}{9}:x=\frac{35}{6}\)
\(x=\frac{35}{9}:\frac{35}{6}\)
\(x=\frac{35}{9}x\frac{6}{35}\)
\(x=\frac{2}{3}\)
b) \(\left(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}\right)x10-X=0\)
\(\left(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+.....+\frac{1}{5}-\frac{1}{6}\right)x10-X=0\)
\(\left(\frac{1}{1}-\frac{1}{6}\right)x10-X=10\)
\(\frac{5}{6}x10-X=0\)
\(X=\frac{5}{6}x10=\frac{25}{3}\)
Đúng nha !!!!
1/a/\(\frac{5}{7}\cdot4:\frac{5}{9}=\frac{20}{7}:\frac{5}{9}=\frac{20}{7}\cdot\frac{9}{5}=\frac{36}{7}\)
b/\(8\cdot\frac{2}{3}:\frac{1}{2}=\frac{16}{3}:\frac{1}{2}=\frac{16}{3}\cdot\frac{2}{1}=\frac{32}{3}\)
c/\(6:\frac{3}{5}-\frac{7}{6}\cdot\frac{6}{7}=6\cdot\frac{5}{3}-1=10-1=9\)
2/a/\(\frac{35}{9}:x=\frac{35}{6}\)
\(x=\frac{35}{9}:\frac{35}{6}=\frac{35}{9}\cdot\frac{6}{35}\)
\(x=\frac{2}{3}\)
b/\(\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}\right)\cdot10-x=0\)
\(\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}\right)\cdot10-x=0\)
\(\left(\frac{30}{60}+\frac{10}{60}+\frac{5}{60}+\frac{2}{30}\right)\cdot10-x=0\)
\(\frac{47}{60}\cdot10-x=0\)
\(\frac{47}{6}-x=0\)
\(x=\frac{47}{6}-0\)
\(x=\frac{47}{6}\)
\(\left(\frac{a}{b}+\frac{5}{7}\right).\frac{4}{5}=\frac{38}{35}\)
\(\left(\frac{a}{b}+\frac{5}{7}\right)=\frac{38}{35}:\frac{4}{5}\)
\(\left(\frac{a}{b}+\frac{5}{7}\right)=\frac{19}{14}\)
\(\frac{a}{b}=\frac{19}{14}-\frac{5}{7}\)
\(\frac{a}{b}=\frac{9}{14}\)
Vậy \(\frac{a}{b}=\frac{9}{14}\)