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\(a,\frac{1}{2\times3}+\frac{1}{3\times4}+\frac{1}{4\times5}+\frac{1}{5\times6}=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\)
\(=\frac{1}{2}-\frac{1}{6}=\frac{1}{3}\)
\(b,\left(1-\frac{1}{2}\right)\times\left(1-\frac{1}{3}\right)\times\left(1-\frac{1}{4}\right)=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\)
\(=\frac{1\times2\times3}{2\times3\times4}=\frac{1}{4}\)
\(a,\frac{2}{5}+\frac{1}{6}+\frac{3}{5}\)
\(=\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{1}{6}\)
\(=1+\frac{1}{6}\)
\(=\frac{7}{6}\)
Hok tốt!~
4/5 : 2/9 x 2/9 : 4/5
= 4/5 x 9/2 x 2/9 x 5/4
= ( 4/5 x 5/4 ) x ( 9/2 x 2/9 )
= 1x1
= 1
\(\frac{4}{5}:\frac{2}{9}\times\frac{2}{9}:\frac{4}{5}\)
\(=\frac{4}{5}\times\frac{9}{2}\times\frac{2}{9}\times\frac{5}{4}\)
\(=\left(\frac{4}{5}\times\frac{5}{4}\right)\times\left(\frac{2}{9}\times\frac{9}{2}\right)\)
\(=1\times1\)
\(=1\)
a) \(\frac{13}{19}+\frac{18}{19}+\frac{19}{19}=\left(\frac{13}{19}+\frac{17}{19}\right)+\frac{18}{19}=\frac{20}{19}+\frac{18}{19}=\frac{48}{19}\)
b) \(\frac{3}{5}+\frac{3}{16}+\frac{13}{16}=\left(\frac{3}{16}+\frac{13}{16}\right)+\frac{3}{5}=1+\frac{3}{5}=\frac{5}{5}+\frac{3}{5}=\frac{8}{5}\)
a) \(\frac{13}{19}+\frac{18}{19}+\frac{17}{19}\)
= \(\frac{31}{19}+\frac{17}{19}\)
= \(\frac{48}{19}.\)
b) \(\frac{3}{5}+\frac{3}{16}+\frac{13}{16}\)
= \(\frac{3}{5}+\left(\frac{3}{16}+\frac{13}{16}\right)\)
= \(\frac{3}{5}+\frac{16}{16}\)
= \(\frac{3}{5}+1\)
= \(\frac{3}{5}.\)
a, \(\frac{5}{11}\times\frac{7}{25}+\frac{15}{11}\times\frac{1}{5}\)
\(=\frac{5}{11}\times\frac{7}{25}+\frac{5}{11}\times\frac{3}{5}\)
\(=\frac{5}{11}\times\left(\frac{7}{25}+\frac{3}{5}\right)\)
\(=\frac{5}{11}\times\frac{22}{25}\)
\(=\frac{2}{5}\)
b, \(\frac{3}{7}\times\frac{25}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\frac{75}{19}-\frac{1}{7}\times\frac{18}{19}\)
\(=\frac{1}{7}\times\left(\frac{75}{19}-\frac{18}{19}\right)\)
\(=\frac{1}{7}\times3\)
\(=\frac{3}{7}\)
1-(1-(1/2 × 3/5 + 1/5 × 1/2 + 2/10 × 1/2 +1/2)
=1-(1-(3/10 + 1/10 + 1/10 + 5/10)
=1-(1-(3+1+1+5/10)
=1-(1- 10/10)
=1-(1-1)
=1-0
=1
\(1-\left[1-\left(\frac{1}{2}\times\frac{3}{5}+\frac{1}{5}\times\frac{1}{2}+\frac{2}{10}\times\frac{1}{2}+\frac{1}{2}\right)\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\left(\frac{3}{5}+\frac{1}{5}+\frac{2}{10}+\frac{1}{2}\right)\right\}\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\left(\frac{6}{10}+\frac{2}{10}+\frac{2}{10}+\frac{5}{10}\right)\right\}\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\left(\frac{6+2+2+5}{10}\right)\right\}\right]\)
\(=1-\left[1-\left\{\frac{1}{2}\times\frac{3}{2}\right\}\right]\)
\(=1-\left[1-\frac{3}{4}\right]\)
\(=1-\frac{1}{4}\)
\(=\frac{3}{4}\)
bài 1
\(\frac{13}{19}+5=\frac{108}{19}\)
Bài 2 sai de thi phai
Bài 3
Giải
Số phần bạn A làm xong kế hoạch là:
\(\frac{3}{5}+\frac{1}{4}=\frac{17}{20}\)
Vậy còn \(\frac{3}{20}\)phần kế hoạch chưa làm
Bài 4
\(\frac{47}{15}+\frac{40}{17}-\frac{4}{30}-\frac{6}{17}\)
\(=\left(\frac{40-6}{17}\right)+\left(\frac{47-2}{15}\right)=5\)
Bài 5
a)
\(\frac{1}{2}-\frac{1}{3}=\frac{1}{6}\)VÀ \(\frac{1}{2x3}=\frac{1}{6}\)
Vạy 2 gia trị bằng nhau
b)
\(\frac{2}{3x5}=\frac{2}{15}\)Và \(\frac{1}{3}-\frac{1}{5}=\frac{2}{15}\)
Vậy 2 giá trị bằng nhau
\(\frac{17}{2}\times\frac{3}{5}+\frac{3}{5}\times\frac{1}{2}+\frac{3}{5}\)
\(=\frac{3}{5}\times\left(\frac{17}{2}+\frac{1}{2}\right)\)
\(=\frac{3}{5}\times9\)
\(=\frac{27}{5}\)
Ai Fan anh Kha diem danh
\(\frac{17}{2}\times\frac{3}{5}+\frac{3}{5}\times\frac{1}{2}+\frac{3}{5}\)
\(=\frac{3}{5}\times\left(\frac{17}{2}+\frac{1}{2}+1\right)\)
\(=\frac{3}{5}\times\left(\frac{17}{2}+\frac{1}{2}+\frac{2}{2}\right)\)
\(=\frac{3}{5}\times\frac{20}{2}\)
\(=\frac{60}{10}=6\)
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