Question

Calculați sumele:
A) 1+2+3+...+99+100
B)2+4+6+8+...+28
C)3+6+9+12+...+42+45
Repede va roggg

Answer 1

a)

1 + 2 + .. + 100 = 100×101 : 2 = 50×101 = 5050

b)

2 + 4 + .. + 28 = 2·(1 + 2 + .. +14) = 2×14×15 : 2 = 210

c)

3 + 6 + .. + 45 = 3·(1 + 2 + .. +15) = 2×15×16 : 2 = 240