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\(a.32,5-3\cdot0,87=32,5-2,61=29,89\)
\(8,5\cdot\left(1\dfrac{1}{2}+\dfrac{4}{4}\right):5=8,5\cdot\left(\dfrac{3}{2}+\dfrac{4}{4}\right):5\\ =8,5\cdot\left(\dfrac{6}{4}+\dfrac{4}{4}\right):5\\ =8,5\cdot\dfrac{10}{4}:5\\ =\dfrac{85}{4}:5\\ =\dfrac{17}{4}\)
\(b.30,96-6,45+14,4:3=30,96-6,45+4,8\\ =29,31\)
\(\dfrac{2}{5}\cdot\left(\dfrac{4}{5}-\dfrac{1}{2}\right)=\dfrac{2}{5}\cdot\left(\dfrac{8}{10}-\dfrac{5}{10}\right)\\ =\dfrac{2}{5}\cdot\dfrac{3}{10}=\dfrac{3}{25}\)
bài 2
\(a.2,5\cdot12,5\cdot8\cdot0,4=\left(2,5\cdot0,4\right)\left(12,5\cdot8\right)\\ =1\cdot100=100\)
b,\(\dfrac{12}{15}\cdot\dfrac{5}{6}\cdot\dfrac{3}{20}\cdot\dfrac{32}{5}=\dfrac{12\cdot5\cdot3\cdot32}{15\cdot6\cdot20\cdot5}\\ =\dfrac{3\cdot4\cdot5\cdot3\cdot4\cdot8}{3\cdot5\cdot2\cdot3\cdot5\cdot4\cdot5}=\dfrac{16}{25}\)
Bài 1:
a) \(32.5-3\cdot0.87=32.5-2.61=29.89\)
\(8.5\cdot\left(1\dfrac{1}{2}+\dfrac{4}{4}\right):5=8.5\cdot\dfrac{5}{2}:5=\dfrac{17}{2}\cdot\dfrac{5}{2}:5=\dfrac{85}{4}\cdot\dfrac{1}{5}=\dfrac{17}{4}\)
\(\frac{5}{12}\times\frac{2}{3}+\frac{2}{3}\times\frac{7}{12}+\frac{1}{3}\)
\(=\frac{2}{3}\times\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{1}{3}\)
\(=\frac{2}{3}\times1+\frac{1}{3}\)
\(=\frac{2}{3}+\frac{1}{3}\)
\(=1\)
\(\frac{5}{12}\times\frac{2}{3}+\frac{2}{3}\times\frac{7}{12}+\frac{1}{3}=\frac{2}{3}\times\left(\frac{5}{12}+\frac{7}{12}\right)+\frac{1}{3}\)
\(=\frac{2}{3}\times\frac{12}{12}+\frac{1}{3}=\frac{2}{3}\times1+\frac{1}{3}=\frac{2}{3}+\frac{1}{3}=\frac{3}{3}=1\)
\(\frac{2}{3}\cdot\frac{4}{7}+\frac{2}{3}\cdot\frac{3}{7}\)
=\(\frac{2}{3}\left(\frac{4}{7}+\frac{3}{7}\right)\)
= \(\frac{2}{3}\cdot1\)
= \(\frac{2}{3}\)
Có: \(\dfrac{7}{6}\times\dfrac{1}{2}+\dfrac{7}{6}\times\dfrac{3}{4}+\dfrac{7}{6}+\dfrac{15}{4}\)
\(=\dfrac{7}{6}\times\left(\dfrac{1}{2}+\dfrac{3}{4}+1\right)+\dfrac{15}{4}\)
\(=\dfrac{7}{6}\times\dfrac{9}{4}+\dfrac{15}{4}\)
\(=\dfrac{63}{24}+\dfrac{90}{24}=\dfrac{51}{8}\)
7/6 × 1/2 + 7/6 × 3/4 + 7/6 × 15/4
= 7/6 × (1/2 + 3/4 + 15/4)
= 7/4 × (2/4 + 3/4 + 15/4)
= 7/4 × 5
= 35/4
\(2\frac{1}{2}+3\frac{1}{18}+7\frac{5}{36}\)
\(=\frac{5}{2}+\frac{55}{18}+\frac{257}{36}\)
\(=\frac{90}{36}+\frac{110}{36}+\frac{257}{36}\)
\(=\frac{90+110+257}{36}=\frac{457}{36}\)
\(2\frac{1}{2}+3\frac{1}{18}+7\frac{5}{36}\)
\(=\left(2+3+7\right)\left(\frac{1}{2}+\frac{1}{18}+\frac{5}{36}\right)\)
\(=12\left(\frac{1}{2}+\frac{1}{18}+\frac{5}{36}\right)\)
\(=12\frac{25}{36}=\frac{457}{36}\)
\(\frac{7}{19}\times\frac{1}{3}+\frac{7}{19}\times\frac{2}{3}\)
\(=\frac{7}{19}\times\left(\frac{1}{3}+\frac{2}{3}\right)\)
\(=\frac{7}{19}\times1\)
\(=\frac{7}{19}\)
`a)` Diện tích tam giác đó là:
\(\dfrac{2}{7}\times\dfrac{2}{3}:2=\dfrac{2}{21}(cm^2)\)
`b)` Đổi `2 dm=20 cm`
Diện tích hình thang đó là:
\((20+15)\times12:2=210(cm^2)\)
Bạn lên máy tính hoạc calculator nha
HT
875,5*0.10=87.55
567.892*0.001=0.567892
8456,8458*0.01=84.568458
lớp 6 cân tất