## Aptitude question and answer on Average

 33 The average of the first five multiples of 9 is: A.    20 B.    27 C.    28 D.    30 Answer : B.   27 Explanation: Required average = (total sum of multiple of 9)/5 = $(9+18+27+36+45)\over5$ = 27 Discuss 34 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?   A.    65 B.    75 C.    74 D.    64 Answer : B.   75 Explanation: Total age of 50 students and 1 teacher = $25\times51$= 1275 Total age of the students = $24\times50$ = 1200. ( Average age reduces by 1 when teachers age is not included ) Therefore the age of the teacher is 1275 – 1200 = 75 years. Discuss 35 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: A.    20 B.    21 C.    28 D.    32 Answer : C.  28 Explanation: 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. Now, $=>9x+100 = 10\times(x+8)$ Or, $9x+100 = 10x+80$ Or, $x = 100-80$ Or, x = 20 New average = $(x+8) = 28$  runs. Discuss