Question

Repede : S = 3 + 6 + 9 + 12 + ... + 60 : Punctele sunt indicatii ca trebuie pana la 60.

Answer 1

3+6+9+....+60
3•(1+2+3+...+20)
3•[20•(20+1):2]
3•(20•21:2)
3•(10•21)
3•210
=630