Question

2. Calculați următoarele sume:
a) 5+6+7+...+50;
b) 25+26+27+...+325;
c) 30+31+32+...+1985;
d) 50+51+52+...+2020.

Answer 1

2. Calculați următoarele sume:

a) 5+6+7+...+50=5×45+1+2+...45=

225+45×46/2=225+1035=1260

b) 25+26+27+...+325=25×300+1+2+...+300=

7500+300×301/2=7500+150×301=

7500+45150=52650

c) 30+31+32+...+1985=30×1955+1955×1956/2=

58650+1911990=1970640

d) 50+51+52+...+2020=50×1970+1970×1971/2=

98500+1941435=2039935