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37 x 13 - \(\frac{13}{24}\) + 37 x 12
= 37 x ( 13 + 12) - \(\frac{13}{24}\)
= 37 x 25 - \(\frac{13}{24}\)
= 925 - \(\frac{13}{24}\)
= \(\frac{22187}{24}\)
a)<=>2/7:(13/24+5/24) b)<=>15/24-9/24-4/24 c)=7.5.39/13.14.15
<=>2/7:3/4 <=>2/24=1/12 =3/2.3
<=>2/7x4/3 =1/2
<=>8/21
a. \(\frac{2}{7}:\frac{13}{24}+\frac{2}{7}:\frac{5}{24}\)
= \(\frac{2}{7}:\left(\frac{13}{24}+\frac{5}{24}\right)\)
= \(\frac{2}{7}:\frac{3}{4}\)
= \(\frac{8}{21}\)
b. \(\frac{15}{24}-\frac{3}{8}-\frac{1}{6}\)
= \(\frac{15}{24}-\frac{9}{24}-\frac{4}{24}\)
= \(\frac{2}{24}=\frac{1}{12}\)
c. \(\frac{7}{13}.\frac{5}{14}.\frac{39}{15}\)
= \(\frac{7.5.3.13}{13.2.7.3.5}\)
= \(\frac{1}{2}\)
\(\frac{2}{7}:\frac{13}{24}+\frac{2}{7}:\frac{5}{24}\)
\(=\frac{2}{7}x\frac{24}{13}+\frac{2}{7}x\frac{14}{5}=\frac{2}{13}x\frac{24}{7}+\frac{2}{5}x\frac{24}{7}\)
\(=\frac{24}{7}x\left(\frac{2}{13}+\frac{2}{5}\right)=\frac{24}{7}x\frac{36}{65}=\frac{864}{455}\)
\(\frac{1}{4}+\frac{1}{12}+\frac{1}{24}+\frac{1}{40}+\frac{1}{60}+\frac{1}{84}\)
\(=\frac{1}{2}\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}\right)\)
\(=\frac{1}{2}\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}\right)\)
\(=\frac{1}{2}\left(1-\frac{1}{7}\right)\)
\(=\frac{1}{2}.\frac{6}{7}=\frac{3}{7}\)
Đặt \(C=\frac{1}{2}+\frac{1}{12}+\frac{1}{24}+...+\frac{1}{84}\)
\(\Rightarrow\frac{C}{2}=1+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{42}\)
\(\Rightarrow C.\frac{1}{2}=1+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{6.7}\)
\(\Rightarrow C.\frac{1}{2}=1+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{6}-\frac{1}{7}\)
\(\Rightarrow C.\frac{1}{2}=1+\frac{1}{2}-\frac{1}{7}\)
\(\Rightarrow C=\left(1+\frac{1}{2}-\frac{1}{7}\right).2\)
1, =35 x 77-35 x 12+35x35-35 x 18 suy ra =35 x(77-12+35-18)=35 x 82=2870.
2, =2014 x (100-1)=201400-2014=199386.
3,=35x12+65x12+65=12x(65+35)+65=1200+65=1265.
4.=\(\frac{13\times\left(37-1\right)}{12\times\left(37+2\right)}\)=\(\frac{13\times36}{12\times39}=\frac{13\times3\times12}{12\times3\times13}=1\)
tck nha bạn