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a) 333...3 x 999...9
(10 c/s 3) (10 c/s 9)
= 333...3 x (1000...0 - 1)
(10 c/s 3) (10 c/s 0)
= 333...3 x 1000...0 - 333...3
(10 c/s 3) (10 c/s 0)(10 c/s 3)
= 333...3000..0 - 333...3
(10 c/s 3)(10 c/s 0)(10 c/s 3)
= 333....32666...67
(9 c/s 3) (9 c/s 6)
b) lm tương tự câu a
333...333 . 999...999
30 CS 3 30 CS 9
= 333...333 . ( 100...000 - 1 )
30 CS 3 30 CS 0
= 333...3 000...0 - 333...333
30 CS 3 30CS 0 30 CS 3
Đặt phép trừ :
333...333 000..000
- 333...333
333...33 2 666... 667
29 CS3 29 CS 6
Vậy ta được : 333...333 2 666...6 7
29 CS 3 29 CS 6
=>\(\left(\frac{9}{20}+\frac{9}{30}+\frac{9}{4}+111\right)+\frac{9}{2}\left(x+1\right)=\frac{3}{2}\)
=>\(114+\frac{9}{2}\left(x+1\right)=\frac{3}{2}\)
=>\(\frac{9}{2}\left(x+1\right)=\frac{-111}{2}\)
=>x+1=\(-\frac{37}{3}\)
=>x=\(-\frac{40}{3}\)
\(\text{a)}25\%-\frac{3}{2}+0,5.\frac{12}{5}\)
\(=\frac{1}{4}-\frac{3}{2}+\frac{1}{2}.\frac{12}{5}\)
\(=-\frac{5}{8}+\frac{6}{5}\)
\(=-\frac{25}{40}+\frac{48}{40}\)
\(=\frac{23}{40}\)
\(b)0,25.\frac{7}{3}.30.\text{ }0,5.\frac{8}{45}\)
\(=\frac{1}{4}.\frac{7}{3}.30.\frac{1}{2}.\frac{8}{45}\)
\(=\frac{7}{12}.(30.\frac{8}{90})\)
\(=\frac{7}{12}.\frac{8}{3}\)
\(=\frac{14}{9}\)
\(c)\frac{9}{23}.\frac{5}{8}+\frac{9}{23}.\frac{3}{8}-\frac{9}{23}\)
\(=\frac{9}{23}.\left(\frac{5}{8}+\frac{3}{8}-1\right)\)
\(=\frac{9}{23}.0\)
\(=0\)
Bài này hơi rối ha ^ ^
9.3.1001+9,9.30000+ 30.899,9.9
\(=9.3.1001+9.1,1.30.1000+30.899,9.9\)
\(=9.3.1001+9.30.\left(1,1.1000\right)+9.30.899,9\)
\(=9.3.1001+9.3.10.1100+9.3.10.899,9\)
\(=9.3.1001+9.3.11000+9.3.8999\)
\(=9.3\left(1001+11000+8999\right)\)
\(=27.21000=567000\)