Question

1.
a)1+2+3+4+...+100
b)1+2+3+...509
c)2+4+6+...+480
d)3+6+9+...+963

Answer 1

Răspuns:

A) 100.(100+1):2

100.101:2

50.101

5050

Answer 2

Explicație pas cu pas:

a) 100×(100+1)÷2=50×101=5050

b) 509x(509+1)÷2=509×255=129795

c) 2x( 1+2+3...+240)=2× 240×(240+1)÷2=2×120×241=57840

d)3×(1+2....+321)=3×321×(321+1)÷2=155043