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\(\text{Giải:}\)
\(\frac{1}{2}+\frac{3}{4}.\frac{1}{3}=\frac{1}{2}+\frac{3}{12}=\frac{6}{12}+\frac{3}{12}\)\(=\frac{9}{12}\)
\(\frac{2}{3}+\frac{1}{2}-\frac{5}{12}=\frac{8}{12}+\frac{6}{12}-\frac{5}{12}\)\(=\frac{9}{12}\)
\(\text{Học tốt!!!}\)
\(1\frac{1}{2}+1\frac{1}{3}=1\frac{3}{6}+1\frac{2}{6}\)\(=2\frac{5}{6}\)
\(\frac{5}{6}:\frac{3}{8}.\frac{3}{4}=\frac{5}{6}.\frac{8}{3}.\frac{3}{4}\)\(=\frac{5.8.3}{6.3.4}=\frac{120}{72}=\frac{3}{5}\)
\(\text{Học tốt!!}\)
\(\frac{3}{5}.\frac{4}{7}.1.\frac{1}{2}\)
\(=\frac{3.4.1.1}{5.7.1.2}\)
\(=\frac{12}{70}\)
\(=\frac{12:2}{70:2}=\frac{6}{35}\)
\(1\frac{1}{2}\times1\frac{1}{3}\times1\frac{1}{4}\times.....\times1\frac{1}{98}\times1\frac{1}{99}.\)
= \(\frac{3}{2}\times\frac{4}{3}\times\frac{5}{4}\times.....\times\frac{99}{98}\times\frac{100}{99}\)
= \(\frac{3\times4\times5\times....\times99\times100}{2\times3\times4\times.....\times98\times99}\)
= \(\frac{100}{2}\)
= \(50\)
(1+1/2)x(1+1/3)x(1+1/4)x....x(1+1/98)x(1+1/99)
=3/2x4/3x5/4x..........x99/98x100/99
=(3x4x5x........x99x100)/2x3x4x........x98x99
Giản ước ta được:
=100/2
=50
bằng 34 nhé
\(M=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\)\(\frac{1}{1+2+3+4+5}\)
\(\Rightarrow M=\frac{1}{2\times\left(1+2\right):2}+\frac{1}{3\times\left(1+3\right):2}+\frac{1}{4\times\left(1+4\right):2}+\frac{1}{5\times\left(1+5\right):2}\)
\(\Rightarrow M=\frac{2}{2\times3}+\frac{2}{3\times4}+\frac{2}{4\times5}+\frac{2}{5\times6}\)
\(\Rightarrow M=2\left(\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}\right)\)
\(\Rightarrow M=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\right)\)
\(\Rightarrow M=2\left(\frac{1}{2}-\frac{1}{6}\right)\Rightarrow M=2\times\frac{1}{3}\Rightarrow M=\frac{2}{3}\)