Question

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

Answer 1

Vedem ca toti termenii sunt multiplii de 3 asa ca fam factor comun 3

3(1+2+3+4+5+6+...+20)=(observam ca in paranteza avem Gaus ) 3×20×21/2=630

Answer 2

Răspuns:

S=3+6+9+12+....+60

(60-3)÷3+1=57÷3+1=19+1=20 nr de termeni

S=[(3+60)×20]÷2

S=63×20÷2

S=630