Ta có :
\(37.12\)
\(=37.\left(3.4\right)\)
\(=\left(37.3\right).4\)
\(=111.4\)
\(=444\)
37 . 12 = 37 . 3 . 4
= (37 . 3) . 4
= 111 . 4
= 444
37 . 3 = 111
37 . 12 = 37 . 3 . 4
37 . 12 = 111 . 4
37 . 12 = 444
\(37\cdot3=111\)
\(\Leftrightarrow37\cdot3\cdot4=111\cdot4\)
\(\Leftrightarrow37\cdot12=444\)