Cách 1:
5 + 5 + 5 + 5 + 10 + 10
= 10 + 5 + 5 + 10 + 10
= 15 + 5 + 10 + 10
= 20 + 10 + 10
= 30 + 10
= 40
Cách 2:
5 + 5 + 5 + 5 + 10 + 10
= (5 . 4 ) + (10 . 2)
= 20 + 20
= 20 . 2
= 40
Cách 3:
5 + 5 + 5 + 5 + 10 + 10
= (5 + 5) + (5 + 5) + 10 + 10
= 10 + 10 + 10 + 10
= 10 . 4
= 40
\(5+5+5+5+10+10\)
\(=5.4+10.2\)
\(=20+20\)
\(=20.2\)
\(=40\)