Tìm số tự nhiên X biết \(1\frac{1}{5}\times1\frac{1}{6}\times1\frac{1}{7}\times...\times1\frac{1}{2014}\) =X
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\(1\frac{1}{3}.1\frac{1}{4}.1\frac{1}{5}.1\frac{1}{6}.1\frac{1}{7}.1\frac{1}{8}.1\frac{1}{9}.1\frac{1}{10}.1\frac{1}{11}\)
\(=\frac{4}{3}.\frac{5}{4}.\frac{6}{5}.\frac{7}{6}.\frac{8}{7}.\frac{9}{8}.\frac{10}{9}.\frac{11}{10}.\frac{12}{11}\)
\(=\frac{12}{3}=4\)
1 1/13 x 1 1/14 x ........... x 1 1/2014 = 14/13 x 15/14 x ...... x 2015/2014 = (14 x 15 x ....x 2014) x 2015/( 14 x 15 x .......x2014) x 13 = 2015/13
\(=\frac{16}{15}\times\frac{17}{16}\times\frac{18}{17}\times...\times\frac{2010}{2009}\times\frac{2011}{2010}\)
\(=\frac{1}{15}\times2011\)
\(=\frac{2011}{15}\)
Ta có : \(1\frac{1}{2}\times1\frac{1}{3}\times1\frac{1}{4}\times.....\times1\frac{1}{2017}\)
\(=\frac{3}{2}.\frac{4}{3}.\frac{5}{4}.....\frac{2018}{2017}\)
\(=\frac{2018}{2}=1009\)
\(1\frac{1}{2}\times1\frac{1}{3}\times1\frac{1}{4}\times....\times1\frac{1}{2017}\)
\(=\frac{3}{2}\times\frac{4}{3}\times\frac{5}{4}\times...\times\frac{2018}{2017}\)
\(=\frac{3\times4\times5\times.....\times2018}{2\times3\times4\times.....\times2017}\)
\(=\frac{2018}{2}=1009\)
a)
12,5 x 40,7 + 59,3 x12,5
= 12,5 x ( 40,7 + 59,3)
= 12,5 x 100
= 1250
a]
12,5 x 40,7 + 59,3 x 12,5
= 12,5 x [ 40,7 + 59,3]
= 12,5 x 100 = 125
b]
1,9 + 1,8 + 1,7 + 1,6 + 1,5 , 1,4 , 1,3 , 1,2 , 1,1
= [1,9 + 1,1 ] + [1,8 + 1,2 ] + [ 1,7 + 1,3 ] + [1,6 + 1,4 ] + 1,5
= [3 + 3 + 3 + 3 ]+ 1,5
= 12 + 1,5
=13,5
\(=\frac{3}{2}\times\frac{4}{3}\times.............\times\frac{2016}{2015}\)
\(=\frac{3\times4\times.............\times2016}{2\times3\times..............\times2015}\)
\(=\frac{2016}{2}=1008\)
\(1\frac{1}{5}\)X \(1\frac{1}{6}\) X \(1\frac{1}{7}\) X \(...\)X \(1\frac{1}{2014}\) = x
x = \(\frac{6}{5}\) X \(\frac{7}{6}\) X \(\frac{8}{7}\) X \(...\)X \(\frac{2015}{2014}\)
x = \(\frac{6\cdot7\cdot8\cdot...\cdot2015}{5\cdot6\cdot7\cdot...2014}\)
x = \(\frac{2015}{5}\)
x = 403
6/5 × 7/6 × 8/7 × ... × 2015/2014 = x
2015/5 = x
x = 403
Vậy x = 403
Ủng hộ mk nha ♡_♥☆_★^_-