Question

Aflati media aritmetica a numerelor a si b,unde a=1 supra 10+2 supra 11+...+1991 supra 2000 si b=9 supra 10+9 supra 11+...+9 supra 2000

Answer 1

 a=1/10+2/11+...+1991/2000
b=9/10+9/11+...+9/2000
(a+b)/2=(1/10+2/11+...+1991/2000 +9/10+9/11+...+9/2000=
=(1/10+9/10+2/11+9/11+.....+1991/2000+9/2000)/2=
=(10/10+11/11+....+2000/2000)/2=
=(1+1+......1)/2=1991/2=995,5

nr termeni =(2000-10+1)=1991