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\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)
\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)
\(=60\times\frac{51}{60}\)
\(=51\)
\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)
\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
\(A=\frac{1}{2}×\frac{3}{4}+\frac{1}{4}×\frac{1}{2}\)
\(A=\frac{1}{2}×\left(\frac{3}{4}+\frac{1}{4}\right)\)
\(A=\frac{1}{2}×\left(\frac{3+1}{4}\right)\)
\(A=\frac{1}{2}×1\)
\(A=\frac{1}{2}\)
\(B=\frac{1212}{2121}×\frac{151515}{161616}\)
\(B=\frac{1212:101}{2121:101}×\frac{151515:10101}{161616:10101}\)
\(B=\frac{12}{21}×\frac{15}{16}\)
\(B=\frac{12×15}{21×16}\)
\(B=\frac{3×4×3×5}{3×7×4×4}\)
\(B=\frac{15}{28}\)
a) 15 / 17 x 4 / 7 + 15 / 17 x 3 / 7
= 15 / 17 x (4 / 7 + 3 / 7)
=15 / 17 x 1=15 / 17
b) 29 / 12 : 1 / 2 - 5 / 12 :1 / 2
=29 / 12 x2 - 5 / 12 x 2
=(29 / 12 - 5 / 12)x2
=2x2=4
a) 15 / 17 x 4 / 7 + 15 / 17 x 3 / 7
= 15 / 17 x (4 / 7 + 3 / 7)
=15 / 17 x 1=15 / 17
b) 29 / 12 : 1 / 2 - 5 / 12 :1 / 2
=29 / 12 x2 - 5 / 12 x 2
=(29 / 12 - 5 / 12)x2
=2x2=4
chúc bạn học tốt !
Bài làm
\(\frac{7}{15}x\frac{3}{8}+\frac{7}{15}x\frac{5}{8}\)
= \(\frac{7}{15}x\left(\frac{3}{8}+\frac{5}{8}\right)\)
= \(\frac{7}{15}x\frac{8}{8}\)
= \(\frac{7}{15}x1\)
= \(\frac{7}{15}\)
# Chúc bạn học tốt #
\(\frac{7}{15}\cdot\frac{3}{8}+\frac{7}{15}\cdot\frac{5}{8}\)
\(=\frac{7}{15}\cdot(\frac{3}{8}+\frac{5}{8})\)
\(=\frac{7}{15}\cdot1=\frac{7}{15}\)
a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\))
= 60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)
= 35 + 16
= 51
a,\(60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)\(=\frac{60\times7}{12}+\frac{60\times4}{15}\)
\(=\frac{12\times5\times7}{12}+\frac{15\times4\times4}{15}\)
\(=5\times7+4\times4\)
\(=35+16\)
\(=51\)
b, \(\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times...\times\frac{8}{9}\)\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)
\(=\frac{1}{9}\)
\(\dfrac{5}{6}\times\dfrac{7}{5}+\dfrac{5}{6}:\dfrac{15}{3}+\dfrac{5}{6}\times\dfrac{3}{5}-\dfrac{5}{6}\\ =\dfrac{5}{6}\times\dfrac{7}{5}+\dfrac{5}{6}\times\dfrac{1}{5}+\dfrac{5}{6}\times\dfrac{3}{5}-\dfrac{5}{6}\\ =\dfrac{5}{6}\times\left(\dfrac{7}{5}+\dfrac{1}{5}+\dfrac{3}{5}-1\right)\\ =\dfrac{5}{6}\times\dfrac{6}{5}=1\)
a) 15/3 x 7/5 + 7/5 x 10/3 + 7/5
= (15/3 + 10/3 + 1) x 7/5
= 28/3 x 7/5
= 196/15
c) 2009 + 3567 + 6433 - 1009
= (2009 - 1009 ) + (3567 + 6433)
= 1000 + 10000
= 11000
\(\frac{15}{3}\)x\(\frac{7}{5}+\frac{7}{5}\)x\(\frac{10}{3}+\frac{7}{5}\)
= \(\frac{15}{3}\)x \(\frac{7}{5}+\frac{7}{5}\)x \(\frac{10}{3}+\frac{7}{5}x1\)
=\(\left(\frac{15}{3}+\frac{10}{3}+1\right)\)x \(\frac{7}{5}\)
= \(\frac{100}{3}\)x \(\frac{7}{5}\)
=\(\frac{140}{3}\)
\(\frac{1212}{1717}\)x \(\frac{165165}{132132}\)x\(\frac{515151}{515151}\)
= \(\frac{12}{17}\)x \(\frac{165}{132}\)x \(\frac{51}{51}\)
= \(\frac{12}{17}\)x\(\frac{165}{132}\)x 1
= \(\frac{165}{187}\)
2009 + 3567 + 6433 - 1009
= ( 2009 - 1009 ) + (3567 +6433 )
=1000 + 10000
= 11000