a, 9/1 * 3/8 + 3/8 * 9/7
b, 4/5 * 7/10 - 1/9 * 4/5
C1:nhân chia trước cộng trừ sau
C2:a,3,8x(9,1+9,7)=3,8x18,8=?
b,b, 4/5 * 7/10 - 1/9 * 4/5=4/5x(7/10-1/9)=?
Cách 1: \(a,\frac{9}{1}x\frac{3}{8}+\frac{3}{8}x\frac{9}{7}\)
\(=\frac{3}{8}x\left(\frac{9}{1}+\frac{9}{7}\right)\)
\(=\frac{3}{8}x\frac{72}{7}\)
\(=\frac{216}{56}=\frac{27}{7}\)
Cách 2: \(a,\frac{9}{1}x\frac{3}{8}+\frac{3}{8}x\frac{9}{7}\)
\(=\frac{27}{8}+\frac{27}{56}\)
\(=\frac{189}{56}+\frac{27}{56}\)
\(=\frac{216}{56}=\frac{27}{7}\)
\(b,\) Cách 1: \(\frac{4}{5}x\frac{7}{10}-\frac{1}{9}x\frac{4}{5}\)
\(=\frac{4}{5}x\left(\frac{7}{10}-\frac{1}{9}\right)\)
\(=\frac{4}{5}x\left(\frac{63}{90}-\frac{10}{90}\right)\)
\(=\frac{4}{5}x\frac{53}{90}\)
\(=\frac{2}{5}x\frac{53}{45}\)
\(=\frac{106}{225}\)