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A=(6 : 35−116 x 67) : (415 x 1011+5211)A=(6 : 35−116 x 67) : (415 x 1011+5211)
A=(6 : 35−76 x 67) : (215 x 1011+5711)A=(6 : 35−76 x 67) : (215 x 1011+5711)
A=(10−1) : (4211+5711)A=(10−1) : (4211+5711)
A=9 : 9A=9 : 9
A=1
\(a.\frac{19}{5}\cdot\frac{4}{7}+\frac{3}{7}\cdot\frac{19}{5}-\frac{4}{5}\)
\(=\frac{19}{5}\cdot\left(\frac{4}{7}+\frac{3}{7}\right)-\frac{4}{5}\)
\(=\frac{19}{5}\cdot1-\frac{4}{5}\)
\(=\frac{19}{5}-\frac{4}{5}=\frac{15}{5}=3\)
\(b.2\frac{2}{7}\cdot5\frac{2}{5}+\frac{16}{7}\cdot1\frac{3}{5}+\frac{1}{2}\)
\(=\frac{16}{7}\cdot\frac{27}{5}+\frac{16}{7}\cdot\frac{8}{5}+\frac{1}{2}\)
\(=\frac{16}{7}\cdot\left(\frac{27}{5}+\frac{8}{5}\right)+\frac{1}{2}\)
\(=\frac{16}{7}\cdot7+\frac{1}{2}\)
\(=16+\frac{1}{2}=\frac{33}{2}\)
\(c.\frac{3}{7}\cdot3\frac{3}{4}-\frac{3}{7}\cdot\frac{5}{4}-\frac{1}{4}\)
\(=\frac{3}{7}\cdot\frac{15}{4}-\frac{3}{7}\cdot\frac{5}{4}-\frac{1}{4}\)
\(=\frac{3}{7}\cdot\left(\frac{15}{4}-\frac{5}{4}\right)-\frac{1}{4}\)
\(=\frac{3}{7}\cdot\frac{5}{2}-\frac{1}{4}\)
\(=\frac{15}{14}-\frac{1}{4}=\frac{23}{28}\)
Chú ý: \(\cdot:\times\)
trả lời:
B = 7x( 5/2x7 + 4/7x11 + 3/11x14 + 1/14x15 + 13/15x28 )
B = 7x(1/2 - 1/7 + 1/7 - 1/11 +....+ 1/15 - 1/28)
B = 7x(1/2 - 1/28)
B = 7x13/28
B = 13/4
Bàì làm:
\(B=\frac{5}{2.1}+\frac{4}{1.11}+\frac{3}{11.2}+\frac{1}{2.15}+\frac{13}{15.4}\)
\(B=7.\left(\frac{5}{2.7}+\frac{4}{7.11}+\frac{3}{11.14}+\frac{1}{14.15}+\frac{13}{15.28}\right)\)
\(B=7.\left(\frac{1}{2}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{14}+\frac{1}{14}-\frac{1}{15}+\frac{1}{15}-\frac{1}{28}\right)\)
\(B=7.\left(\frac{1}{2}-\frac{1}{28}\right)\)
\(B=7.\frac{13}{28}\)
\(B=\frac{13}{4}\)
Bài 1:
a) \(2\frac{1}{4}+1\frac{1}{2}-1\frac{4}{5}\)
=\(\frac{9}{4}\)+\(\frac{3}{2}\)-\(\frac{9}{5}\)
=\(\frac{45}{20}+\frac{30}{20}-\frac{36}{20}\)
=\(\frac{39}{20}\)
b) \(2\frac{2}{3}\times3\frac{1}{4}:2\frac{3}{4}\)
\(\frac{8}{3}\times\frac{13}{4}:\frac{11}{4}\)
=\(\frac{8}{3}\times\frac{13}{4}\times\frac{4}{11}\)
=\(\frac{104}{33}\)
Bài 2:
a) \(\frac{7}{9}+\frac{4}{5}+\frac{11}{9}+\frac{6}{5}\)
=\(\left(\frac{7}{9}+\frac{11}{9}\right)+\left(\frac{4}{5}+\frac{6}{5}\right)\)
=2+2
=4
b) \(\frac{21}{36}\times\frac{39}{14}\times\frac{54}{13}\)
=\(\frac{21\times39\times54}{36\times14\times13}\)
=\(\frac{675}{100}\)
\(a,1\dfrac{4}{7}.3\dfrac{4}{11}.3\dfrac{11}{15}.5\dfrac{5}{8}\)
\(=\dfrac{11}{7}.\dfrac{27}{11}.\dfrac{56}{15}.\dfrac{45}{8}\)
\(=\dfrac{11.27.56.45}{7.11.15.8}\)
\(=\dfrac{1.3.7.3}{1.1.1.1}\)
\(=63\)
\(b,\dfrac{3}{4}.1\dfrac{1}{2}+\dfrac{3}{4}.\dfrac{1}{2}\)
\(=\dfrac{3}{4}.\left(1\dfrac{1}{2}+\dfrac{1}{2}\right)\)
\(=\dfrac{3}{4}.2\)
\(=\dfrac{3}{2}\)