Question

calculați suma lui gauss:a 1+2+3...80 b. 2+4+6 +....100 c. 1+3+5...+99 d.3+7+11+15....+43

Answer 1

a. 1+2+3...80 = 80x81/2=3240

(b. 2+4+6 +....100=2(1+2+3+...+50)=2x50*51/2=2550

c. 1+3+5...+99 = (1+99)*50/2=2500
3-1=2 
(99-1):2+1=50 numere

d.3+7+11+15....+43=(3+43)*10/2+23=253
7-3=4
(43-3):4+1=11 numere
numarul din mijloc 3+4*5=23