Question

Tính bằng cách thuận tiện

\(\frac{12}{23}\times\frac{9}{28}+\frac{11}{23}\times\frac{9}{28}=\)

\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2=\)

Answer 1

Câu 1:\(\frac{12}{23}\times\frac{9}{28}+\frac{11}{23}\times\frac{9}{28}\)

\(=\frac{9}{28}\times\left(\frac{12}{23}+\frac{11}{23}\right)\)

\(=\frac{9}{28}\times\frac{23}{23}\)

\(=\frac{9}{28}\times1\)

\(=\frac{9}{28}\)

Câu 2:

\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2\)

\(=\left(3+2+2+3\right)+\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)\)

\(=10+\frac{9}{9}\)

\(=10+1\)

\(=11\)

Answer 2

\(\frac{12}{23}x\frac{9}{28}+\frac{11}{23}x\frac{9}{28}=\)\(\left(\frac{12}{23}+\frac{11}{23}\right)x\frac{9}{28}\)\(=\) \(1x\frac{9}{28}=\frac{9}{28}\)

\(3+\frac{1}{9}+\frac{3}{9}+2+\frac{5}{9}+3+2\)\(=\) \(\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)+\left(3+2+3+2\right)\)\(=\) \(1+3+2+3+2=\)\(11\) 

  

Answer 3

\(\frac{12}{23}\times\frac{9}{28}+\frac{13}{23}\times\frac{9}{28}=\left(\frac{12}{23}+\frac{13}{23}\right)\times\frac{9}{28}\)

                                         \(=\) \(\frac{25}{23}\times\frac{9}{28}\)

                                         \(=\frac{225}{664}\)

Answer 4

\(=11\)

Answer 5

\(\frac{9}{28}.\left(\frac{12}{23}+\frac{11}{23}\right)=\frac{9}{28}.1=\frac{9}{28}\)

\(\left(3+2+3+2\right)+\left(\frac{1}{9}+\frac{3}{9}+\frac{5}{9}\right)\) \(=10+1=11\)