The average age of group of 10 students is 15 years. When 5 new students joined the group, the average age rise by 1 year. The average age (in years) of the new student is :
18 years
17 years
16 years
None of these
The value of (-11)+(-12)+(+13)+ --------(-110) is :
-5050
-6050
-7070