Question

Answer 1

Goi thoi gian nguoi thu nhat, nguoi thu hai lam lan luot la a;b ( a;b > 0 )

1 gio nguoi thu nhat, thu hai lam duoc lan luot 1/a ; 1/b gio 

2 nguoi lam chung trong 3 gio 45 phut => 1/a + 1/b = 4/15

2 nguoi lam 3 gio thi nguoi thu nhat dieu di lam viec khac, nguoi thu 2 lam them 2 gio nua 

=> 3/a + 5/b = 1 

=> \(\left\{{}\begin{matrix}\dfrac{1}{a}+\dfrac{1}{b}=\dfrac{4}{15}\\\dfrac{3}{a}+\dfrac{5}{b}=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}a=6\\b=10\end{matrix}\right.\left(tm\right)\)