Tính bằng cách thuận tiện nhất:
\(3x\dfrac{4}{15}+2x\dfrac{4}{15}-5x\dfrac{4}{15}\)
ĐỀ BÀI CÓ SẴN MN GIÚP EM NHÉ
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a) \(\dfrac{16}{15}+\dfrac{7}{15}+\dfrac{4}{15}=\left(\dfrac{16}{15}+\dfrac{4}{15}\right)+\dfrac{7}{15}=\dfrac{20}{15}+\dfrac{7}{15}=\dfrac{27}{15}\)
b) \(\dfrac{5}{17}+\dfrac{7}{17}+\dfrac{13}{17}=\dfrac{5}{17}+\left(\dfrac{7}{17}+\dfrac{13}{17}\right)=\dfrac{5}{17}+\dfrac{20}{17}=\dfrac{25}{17}\)
1.
=2/5 x 12/3 + 2/5 x 15/3 + 2/5 x 1
= 2/5 x (12/3 + 15/3 + 1)
=2/5 x 1
=2/5
2.a=1;2
Lời giải:
$=\frac{21\times 2\times 12-42\times 12}{15+38:19}+16:4+16$
$=\frac{42\times 12-42\times 12}{15+38:19}+4+16$
$=\frac{0}{15+38:9}+4+16=0+4+16=20$
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{5\times4\times13}{13\times5\times3}=\dfrac{4}{3}\\ b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\dfrac{3}{7}\times\dfrac{7}{5}+\dfrac{5}{2}\times\dfrac{7}{5}=\dfrac{3}{5}+\dfrac{7}{2}=\dfrac{6}{10}+\dfrac{35}{10}=\dfrac{41}{10}\\ c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
60x [7/12+4/15]
60x153/180
=9180/180
b 1/2x2/3x3/4x4/5x5/6x6/7x7/8x8/9=40320/4032
\(\dfrac{50-\dfrac{4}{15}+\dfrac{2}{15}-\dfrac{2}{17}}{100-\dfrac{8}{15}+\dfrac{4}{15}-\dfrac{4}{17}}\) \(=\dfrac{1.\left(50-\dfrac{4}{15}+\dfrac{2}{15}-\dfrac{2}{17}\right)}{2.\left(50-\dfrac{4}{15}+\dfrac{2}{15}-\dfrac{2}{17}\right)}=\dfrac{1}{2}\)
\(a)\dfrac{599}{1000}+\dfrac{377}{1000}+\dfrac{1}{1000}\\ =\left(\dfrac{599}{1000}+\dfrac{1}{1000}\right)+\dfrac{377}{1000}\\ =\dfrac{600}{1000}+\dfrac{377}{1000}\\ =\dfrac{977}{1000}\\ b)\dfrac{15}{4}+\dfrac{15}{16}+\dfrac{5}{16}\\ =\dfrac{15}{4}+\left(\dfrac{15}{16}+\dfrac{5}{16}\right)\\ =\dfrac{15}{4}+\dfrac{20}{16}\\ =\dfrac{60}{16}+\dfrac{20}{16}\\ =\dfrac{80}{16}=5\)
a: =13/26*9/18*2/3=2/3*1/4=2/12=1/6
b: =44/22*5/15*3/2=2*1/3*3/2=2*1/2=1
\(3\times\dfrac{4}{15}+2\times\dfrac{4}{15}-5\times\dfrac{4}{15}\\ =\dfrac{4}{15}\times\left(3+2-5\right)\\ =\dfrac{4}{15}\times0\\ =0\)