Răspuns :
6 + 12 + 18 + 24 +...+ 354 + 360 =
= 6 × (1 + 2 + 3 + 4 +...+ 59 + 60) =
= 6 × 60 × (60+1) : 2 =
= 6 × 60 × 61 : 2 =
= 6 × 30 × 61 =
= 180 × 61 =
= 10 980
= 6 × (1 + 2 + 3 + 4 +...+ 59 + 60) =
= 6 × 60 × (60+1) : 2 =
= 6 × 60 × 61 : 2 =
= 6 × 30 × 61 =
= 180 × 61 =
= 10 980