Question

Bài 1:

\(a)5\dfrac{1}{20}+\dfrac{8}{9}-\dfrac{15}{25}+\dfrac{75}{-18}\)

\(b)\dfrac{1}{15}+\dfrac{1}{35}+\dfrac{1}{63}+\dfrac{1}{99}+\dfrac{1}{143}\)

\(c)\dfrac{6}{7}+\dfrac{5}{7}:5-\dfrac{8}{9}.\dfrac{6}{7}+\dfrac{5}{8}:5-\dfrac{3}{16}.\left(-2\right)^2\)

Answer 1

a)\(=\dfrac{211}{180}\)

b)\(=\dfrac{5}{39}\)

c)=\(=-\dfrac{65}{168}\)

Answer 2

Câu a:

\(\frac{1}{15}\) + \(\frac{1}{35}\) + \(\frac{1}{63}\) + \(\frac{1}{99}\) + \(\frac{1}{143}\)

= \(\frac{1}{3.5}\) + \(\frac{1}{5.7}\) + \(\frac{1}{7.9}\) + \(\frac{1}{9.11}\) + \(\frac{1}{11.13}\)

= \(\frac12.\left(\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+\frac{2}{11.13}\right)\)

= \(\frac12\).(\(\frac13-\frac15+\frac15-\frac17+\frac17-\frac19+\frac19-\frac{1}{11}+\frac{1}{11}-\frac{1}{13})\)

= \(\frac12\).(\(\frac13\) - \(\frac{1}{13}\))

= \(\frac12\).(\(\frac{13}{39}-\frac{3}{39})\)

= \(\frac12\).\(\frac{10}{39}\)

= \(\frac{5}{39}\)

Answer 3

câu a:

5\(\frac{1}{20}\) + \(\frac89\) - \(\frac{15}{25}\) + \(\frac{75}{-18}\)

= \(\frac{101}{20}\) + \(\frac89\) - \(\frac35\) - \(\frac{75}{18}\)

= \(\frac{909}{180}\) + \(\frac{160}{180}\) - \(\frac{108}{180}\) - \(\frac{750}{180}\)

= \(\frac{1069}{180}\) - \(\frac{108}{180}\) - \(\frac{750}{180}\)

= \(\frac{961}{180}\) - \(\frac{750}{180}\)

= \(\frac{211}{180}\)

Answer 4

Câu c:

\(\frac67+\frac57\) : 5 - \(\frac89\) .\(\frac67\) + \(\frac58:5\) - \(\frac{3}{16}\).(-2)\(^2\)

= \(\frac67\) + \(\frac57\) x \(\frac15\) - \(\frac{16}{21}\) + \(\frac58\times\frac15\) - \(\frac{3}{16}\) .4

= \(\frac67\) + \(\frac17\) - \(\frac{16}{21}\) + \(\frac18\) - \(\frac34\)

= 1 - \(\frac{16}{21}\) + \(\frac18\) - \(\frac34\)

= \(\frac{168}{168}\) - \(\frac{128}{168}\) + \(\frac{21}{168}\) - \(\frac{126}{168}\)

= \(\frac{40}{168}\) + \(\frac{21}{168}\) - \(\frac{126}{168}\)

= \(\frac{61}{168}\) - \(\frac{126}{168}\)

= - \(\frac{65}{168}\)