The average marks obtained by 22 candidate in an examination are 45. The average marks of the first 10 candidates is 55 and those of the last eleven is 40. The number of marks obtained by the eleventh candidate is ?

Given that average marks obtained by 22 students = 45
And average of first 10 students = 55
Average of last 11 students = 40
So using, average = $$\frac{{{\text{sum}}}}{{{\text{number of elements}}}}$$
Sum of marks of all 22 students
= 22 x 45
= 990
Sum of students of first 10 students
= 55 x 10
= 550
Sum of last 11 students
= 11 x 40
= 440
So marks obtained by 11^th student
= 990 - (550 + 440)
= 990 - 990
= 0