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1/2*3+1/3*4+1/4*5 + 1/5*6 + .... + 1/99 * 100
= 1/2 -1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 +..... + 1/99 - 1/100
= 1/2 - 1/100
= 49/100 nha bạn !
1/2x3+1/3x4+1/4x5+1/5x6+....+1/99x100
=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+....+1/99-1/100
=1/2-1/100=49/100
1 ( 131,4 - 80,8 ) : 2,3 + 21,84 x 2 = 50,6 : 2,3 + 43,68 = 22 + 43,68= 65,68
\(\left(1-\frac{1}{2}\right)\cdot\left(1-\frac{1}{3}\right)\cdot\left(1-\frac{1}{4}\right)\cdot\left(1-\frac{1}{5}\right)\cdot....\cdot\left(1-\frac{1}{2003}\right)\cdot\left(1-\frac{1}{2004}\right)\)
\(=\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}\cdot\frac{4}{5}\cdot....\cdot\frac{2002}{2003}\cdot\frac{2003}{2004}\)
\(=\frac{1\cdot2\cdot3\cdot4\cdot....\cdot2002\cdot2003}{2\cdot3\cdot4\cdot5\cdot....\cdot2003\cdot2004}\)
\(=\frac{1}{2004}\)
\(\text{Thực hiện phép tính}\)
\(3\text{ × }\left(\frac{1}{7}+\frac{1}{3}-\frac{3}{14}\right) : \frac{11}{4}\)
\(=3\text{ x }\left(\frac{3}{21}+\frac{7}{21}-\frac{3}{14}\right)\text{ : }\frac{11}{4}\)
\(=3\text{ x }\left(\frac{10}{21}-\frac{3}{14}\right)\text{ : }\frac{11}{4}\)
\(=3\text{ x }\left(\frac{140}{294}-\frac{63}{294}\right)\text{ : }\frac{11}{4}\)
\(=3\text{ x }\frac{77}{294}\text{ : }\frac{11}{4}\)
\(=\frac{231}{294}:\frac{11}{4}\)
\(=\frac{231}{294}\text{ x }\frac{4}{11}\)
\(=\frac{924}{3234}=\text{Phân số này có thể rút gọn đó bạn ! Bạn tự rút gọn nha !}\)
\(\left(\frac{21}{8}+\frac{1}{2}\right)\text{ : }\frac{5}{16}\)
\(=\left(\frac{21}{8}+\frac{4}{8}\right)\text{ : }\frac{5}{16}\)
\(=\frac{25}{8}\text{ : }\frac{5}{16}\)
\(=\frac{25}{8}\text{ x }\frac{16}{5}\)
\(=\frac{400}{40}=10\)
\(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}+\frac{1}{72}+\frac{1}{90}\)
\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+...+\frac{1}{9}-\frac{1}{10}\)
\(=1-\frac{1}{10}=\frac{9}{10}\)
Bạn biết bài này rồi phải không =.="
Tính nhanh :
\(A=\frac{1}{4}+\frac{1}{12}+\frac{1}{24}+\frac{1}{40}+\frac{1}{60}+\frac{1}{84}\)
\(A=2\left(\frac{1}{2\cdot4}+\frac{1}{4\cdot6}+\frac{1}{6\cdot8}+\frac{1}{8\cdot10}+\frac{1}{10\cdot12}+\frac{1}{12\cdot14}\right)\)
\(A=2\left(\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+...+\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}\right)\)
\(A=2\left(\frac{1}{2}-\frac{1}{14}\right)\)
\(A=2\cdot\frac{3}{7}\)
\(A=\frac{6}{7}\)
\(A=\frac{1}{4}+\frac{1}{12}+\frac{1}{24}+\frac{1}{40}+\frac{1}{60}+\frac{1}{84}\)
\(A=\frac{2}{8}+\frac{2}{24}+\frac{2}{48}+\frac{2}{80}+\frac{2}{120}+\frac{2}{168}\)
\(A=\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+\frac{2}{8.10}+\frac{2}{10.12}+\frac{2}{12.14}\)
\(A=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}+\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}\)
\(A=\frac{1}{2}-\frac{1}{14}\)
\(A=\frac{3}{7}\)
_Chúc bạn học tốt_
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\(\frac{6:\frac{3}{5}-1\frac{1}{6}.\frac{6}{7}}{4\frac{1}{5}.\frac{10}{11}+5\frac{2}{11}}=\frac{10-\frac{7}{6}.\frac{6}{7}}{\frac{21}{5}.\frac{10}{11}+\frac{57}{11}}=\frac{10-1}{\frac{42}{11}+\frac{57}{11}}=\frac{9}{9}=1\)
\(=1+\frac{1}{1+\frac{1}{1+\frac{1}{\frac{3}{2}}}}=1+\frac{1}{1+\frac{1}{1+\frac{2}{3}}}=1+\frac{1}{1+\frac{1}{\frac{5}{3}}}=1+\frac{1}{1+\frac{3}{5}}=1+\frac{1}{\frac{8}{5}}=1+\frac{5}{8}=\frac{13}{8}\)