Question

1) 5+10+15+...+625=?
2)Calculati suma numerelor, care impartite la 4 dau catul 15.
Vreau toate rezolvarile.

Answer 1

1) 5+10+15+...+625=?
putem face in 2 metode:
5+10+15+...+625=
=5(1+2+3+...+125)=
=5*125*126:2=
=39375

5+10+15+...+625=
=(625+5)*[(625-5):5+1]:2=
=630*125:2=
=39375

2)N:4=15 , rest <4
=> 4*15+ 0=60
4*15+1=61
4*15+2=62
4*15+3=63
N∈{60,61,62,63}
Suma=60+61+62+63=246