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a \(\dfrac{6}{15}+\dfrac{11}{15}=\dfrac{17}{15}\)
b \(\dfrac{22}{77}-\dfrac{14}{77}=\dfrac{8}{77}\)
c \(\dfrac{11}{13}\times\dfrac{26}{31}=11\times\dfrac{2}{31}=\dfrac{22}{31}\)
d \(\dfrac{1}{2}\times3\times\dfrac{2}{5}=\dfrac{3}{5}\)
a) 47 x 9 = 47 x (10 -1)
= 47 x 10 - 47 x 1 = 470 -47 = 423
24 x 99 = 24 x ( 100 -1)
= 24 x 100 - 24 x 1 = 2400 - 24 = 2376
b) 138 x 9 = 138 x (10 -1)
= 138 x 10 - 138 x 1 = 1380 - 138 = 1242
123 x 99 = 123 x (100 -1)
= 123 x 100 - 123 x 1 = 12300 - 123 = 12177
chữa :
a) \(\frac{6}{25}:\frac{21}{20}=\frac{6}{25}.\frac{20}{21}=\frac{6.20}{25.21}=\frac{3.2.4.5}{5.5.7.3}=\frac{8}{35}\)
\(\frac{11}{3}:\frac{99}{21}-\frac{5}{18}\)
\(=\frac{11}{3}.\frac{21}{99}-\frac{5}{18}=\frac{7}{9}-\frac{5}{18}=\frac{14}{18}-\frac{5}{18}\)
\(=\frac{9}{18}=\frac{1}{2}\)
\(\frac{4}{5}+\frac{16}{5}:\frac{4}{55}\)
\(=\frac{4}{5}+\frac{16}{5}.\frac{55}{4}=\frac{4}{5}+11=\frac{4}{5}+\frac{55}{5}\)
\(=\frac{59}{5}\)
11/3:99/21-5/18 =11/3*21/99-5/18=7/9-5/18=15/18-5/18=10/18=5/9 4/5+16/5:4/55=4/5+16/5*55/4=4/5+44=4/5+220/5=224/5 26:13/17:34/7=26*17/13*34/7=34:34/7 =7
a. 123 x 456 = 56088
b. 26 x 7 + 13 x 26
= 26 x ( 7 + 13 )
= 26 x 20
= 520
c. 1301 x 20028 = 26 056 428
Ok
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