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21+22+23+24+25+26+9+8+7+6+5+4 =180
mình thấy rồng con lon ton làm đúng đấy
\(1,\dfrac{12}{25}+\dfrac{3}{5}+\dfrac{13}{25}=\left(\dfrac{12}{25}+\dfrac{13}{25}\right)+\dfrac{3}{5}=1+\dfrac{3}{5}=\dfrac{8}{5}\\ 2,\dfrac{3}{2}+\dfrac{2}{3}+\dfrac{4}{3}=\dfrac{3}{2}+\left(\dfrac{2}{3}+\dfrac{4}{3}\right)=\dfrac{3}{2}+2=\dfrac{7}{2}\\ 3,\dfrac{3}{2}+\dfrac{7}{5}+\dfrac{3}{4}=\left(\dfrac{3}{2}+\dfrac{3}{4}\right)+\dfrac{7}{5}=\left(\dfrac{6}{4}+\dfrac{3}{4}\right)+\dfrac{7}{5}=\dfrac{9}{4}+\dfrac{7}{5}=\dfrac{45}{20}+\dfrac{28}{20}=\dfrac{73}{20}\)
a.245 x ( 327-18-9) = 245 x 300 = 73500
b. (462 - 62) x 4 = 1600
c. 900 : 9 = 100
d. (12+20) : 4 = 8
245x327-245x18-9x245 462 x 4 - 62 x 4
=245x(327-18-9) = ( 462 - 62) x 4
=245x300 = 400 x 4
=73500 = 1600
35 : 7 - 21 : 7 ( 25 x 36 ) : 9
= ( 35 - 21) : 7 = 900 : 9
= 14 : 7 = 100
= 2
12 : 4 + 20 : 4
= ( 12 + 20 ) : 4
= 32 : 4
= 8
\(a,\frac{12}{25}+\frac{3}{5}+\frac{13}{25}\)
\(=\left(\frac{12}{25}+\frac{13}{25}\right)+\frac{3}{5}\)
\(=\frac{25}{25}+\frac{3}{5}\)
\(=1+\frac{3}{5}\)
\(=\frac{8}{5}\)
\(b,\frac{3}{2}+\frac{2}{3}+\frac{4}{3}\)
\(=\frac{3}{2}+\left(\frac{2}{3}+\frac{4}{3}\right)\)
\(=\frac{3}{2}+2\)
\(=\frac{7}{2}\)
\(c,\frac{3}{5}+\frac{7}{5}+\frac{3}{4}\)
\(=\left(\frac{3}{5}+\frac{7}{5}\right)+\frac{3}{4}\)
\(=2+\frac{3}{4}\)
\(=\frac{11}{4}\)
\(\frac{14}{9}:\frac{13}{12}+\frac{4}{3}:\frac{13}{12}\)
\(=\frac{14}{9}\cdot\frac{12}{13}+\frac{4}{3}\cdot\frac{12}{13}\)
\(=\left(\frac{14}{9}+\frac{4}{3}\right)\cdot\frac{12}{13}\)
\(=\frac{26}{9}\cdot\frac{12}{13}=\frac{8}{3}\)
bằng 3