Aptitude question and answer on Average
The average of the first five multiples of 9 is:
The average age of 50 students and a teacher is 25 years. When the teacher’s age is excluded, the average age decreases by 1 year. What is the age of the teacher?
Ajit has a certain average for 9 innings. In the tenth innings, he scores 100 runs thereby increasing his average by 8 runs. His new average is:
Answer : C. 28
Let Ajit's average be x for 9 innings. So, Ajit scored 9x run in 9 innings.
In the 10th inning, he scored 100 runs then average became (x+8). And he scored \((x+8)\times10\) runs in 10 innings.
\(=>9x+100 = 10\times(x+8)\)
Or, \(9x+100 = 10x+80\)
Or, \(x = 100-80\)
Or, x = 20
New average = \((x+8) = 28\) runs.