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 |
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. |
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. |