tính nhanh
a, 15 * 3 + 15 * 7 + 15
b, 24 * 18 - 24 * 7
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a \(x=\dfrac{2}{15}:\dfrac{4}{15}\)
\(x=\dfrac{2}{15}\times\dfrac{15}{4}\)
\(x=\dfrac{1}{2}\)
b \(\dfrac{7}{24}+x=\dfrac{7}{4}\)
\(x=\dfrac{7}{4}-\dfrac{7}{24}\)
\(x=\dfrac{42}{24}-\dfrac{7}{24}\)
\(x=\dfrac{35}{24}\)
27/15 + 6/8 =51/20
19/24 + 7/18 = 85/72
2/9 - 1/6 = 1/18
8/15 -1/3 = 1/5
a: =6/12*7/14*8/16*9/18=1/2*1/2*1/2*1/2=1/16
b: =4/12*15/3*9/25*24/8
=1/3*3*5*9/25=9/5
câu a :
\(\dfrac{-8}{24}+\dfrac{-4}{12}=\dfrac{-1}{3}+\dfrac{-1}{3}=\dfrac{-2}{3}\)
câu b :
\(\dfrac{-20}{35}+\dfrac{16}{24}=\dfrac{-4}{7}+\dfrac{2}{3}=\dfrac{2}{21}\)
câu c :
\(\dfrac{-3}{9}+\dfrac{-6}{15}=\dfrac{-1}{3}+\dfrac{-2}{5}=\dfrac{-11}{15}\)
câu d :
\(\dfrac{3}{13}-\dfrac{4}{10}=\dfrac{3}{13}-\dfrac{2}{5}=\dfrac{-11}{65}\)
câu e :
\(\dfrac{5}{17}-\dfrac{9}{15}=\dfrac{5}{17}-\dfrac{3}{5}=\dfrac{-26}{85}\)
câu g :
\(\dfrac{9}{18}-\dfrac{6}{15}+\dfrac{3}{-9}=\dfrac{9}{18}-\dfrac{6}{15}+\dfrac{-3}{9}\\ =\dfrac{1}{2}-\dfrac{2}{5}+\dfrac{-1}{3}=\dfrac{-7}{30}\)
câu h :
\(\dfrac{5}{4}-\dfrac{1}{2}+\dfrac{-7}{8}=\dfrac{10}{8}-\dfrac{4}{8}+\dfrac{-7}{8}=\dfrac{-1}{8}\)
a, = 15 x (3+7) + 15 = 15 x 10 + 15 = 150 + 15 = 165
b, = 24 x 18 - 24 x 8 + 24 = 24 x (18-8) + 24 = 24 x 10 + 24 = 240 + 24 = 264
k mk nha
a,15*3+15*7+15
=15*(3+7)
=15*10
=150
b,24*18-24*7
=24*(18-7)
=24*11
=264
tk cho mk nha^-^