Bài 5 :
a) Đổi \(1\dfrac{1}{2}\left(m\right)=\dfrac{3}{2}\left(m\right)\)
Nửa chu vi HCN là :
\(8:2=4\left(m\right)\)
Chiều dài HCN là :
\(\left(4+\dfrac{3}{2}\right):2=\dfrac{11}{4}\left(m\right)\)
Chiều dài rộng HCN là :
\(4-\dfrac{11}{4}=\dfrac{5}{4}\left(m\right)\)
b) Diện tích HCN là :
\(\dfrac{11}{4}x\dfrac{5}{4}=\dfrac{55}{16}\left(m^2\right)\)
Đáp số...
Bài 3 :
\(2\dfrac{3}{4}=\dfrac{2x4+3}{4}=\dfrac{11}{4}\)
\(4\dfrac{3}{5}=\dfrac{4x5+3}{5}=\dfrac{23}{5}\)
\(12\dfrac{11}{13}=\dfrac{12x13+11}{13}=\dfrac{167}{13}\)
\(3\dfrac{4}{5}=\dfrac{3x5+4}{5}=\dfrac{19}{5}\)
\(11\dfrac{12}{13}=\dfrac{11x13+12}{13}=\dfrac{155}{13}\)
\(3\dfrac{3}{5}=\dfrac{3x5+3}{5}\dfrac{18}{5}\)
Bài 4 :
a) \(3\dfrac{3}{4}+1\dfrac{1}{2}\)
\(=\dfrac{14}{4}+\dfrac{3}{2}\)
\(=\dfrac{14}{4}+\dfrac{6}{4}\)
\(=\dfrac{20}{4}\)
\(=5\)
b) \(4\dfrac{5}{8}-1\dfrac{1}{4}\)
\(=\dfrac{37}{8}-\dfrac{5}{4}\)
\(=\dfrac{37}{8}-\dfrac{10}{8}\)
\(=\dfrac{27}{8}\)
c) \(3\dfrac{1}{5}:2\dfrac{1}{3}\)
\(=\dfrac{16}{5}:\dfrac{7}{3}\)
\(=\dfrac{16}{5}x\dfrac{3}{7}\)
\(=\dfrac{16x3}{5x7}\)
\(=\dfrac{48}{35}\)
Bài 2 :
a) \(x-\dfrac{1}{6}=\dfrac{1}{2}+\dfrac{1}{3}\)
\(x-\dfrac{1}{6}=\dfrac{3}{6}+\dfrac{2}{6}\)
\(x-\dfrac{1}{6}=\dfrac{5}{6}\)
\(x=\dfrac{5}{6}+\dfrac{1}{6}\)
\(x=\dfrac{6}{6}\)
\(x=1\)
b) \(x+\dfrac{1}{8}=\dfrac{1}{2}-\dfrac{1}{3}\)
\(x+\dfrac{1}{8}=\dfrac{3}{6}-\dfrac{2}{6}\)
\(x+\dfrac{1}{8}=\dfrac{1}{6}\)
\(x=\dfrac{1}{6}-\dfrac{1}{8}\)
\(x=\dfrac{4}{24}-\dfrac{3}{24}\)
\(x=\dfrac{1}{24}\)
c) \(x:\dfrac{1}{2}=\dfrac{2}{3}x\dfrac{3}{4}\)
\(x:\dfrac{1}{2}=\dfrac{1}{2}\)
\(x=\dfrac{1}{2}x\dfrac{1}{2}\)
\(x=\dfrac{1}{4}\)
Bài 1 :
\(2+\dfrac{3}{4}=\dfrac{8}{4}+\dfrac{3}{4}=\dfrac{11}{4}\)
\(\dfrac{5}{7}:6=\dfrac{5}{7}x\dfrac{1}{6}=\dfrac{5x1}{7x6}=\dfrac{5}{42}\)
\(5+\dfrac{2}{7}=\dfrac{35}{7}+\dfrac{2}{7}=\dfrac{39}{7}\)
\(2-\dfrac{3}{5}=\dfrac{10}{5}-\dfrac{3}{5}=\dfrac{7}{5}\)
\(5:\dfrac{3}{2}=5x\dfrac{2}{3}=\dfrac{5x2}{3}=\dfrac{10}{3}\)
4 và 5
