Question

Calculați:(2+4+6+...+80)÷(1+2+3+...+40)​

Answer 1

2+4+6+….+80 =S1
1+2+3+….+40=S2

S1= {(2+80)x [(80-2):2+1]} :2
S1= 82 x [(78:2+1)]:2
S1= 82 x 40:2
S1=1640

S2= (1+40) x 40 : 2
S2= 41 x 20
S2=820

S1:S2= 1640:820
=2