Calculate your average speed for solving these problems
This article is in continuation to the last article on arithmetic that will aid you in your preparation for government recruitment exams. Here are some practice questions along with solutions on the Average topic.
Model: When the person is added/removed.
Examples
1. Average weight of 25 students of a class is 50 kg. If the weight of the class teacher is included, the average is increased by 1 kg. The weight of the teacher is?
a) 75 kg b) 76 kg c) 77 kg d) 74 kg
Ans: b
Solution: Let the weight of the teacher = x kg
Average = (25 × 50 1 × x)/ 25 1 = 51
=>; 1250 x = 51 × 26
=>; 1250 x = 1326
x = 1326 – 1250 = 76 kg
Shortcut: 25 students teacher
50 kg = 51 kg
When the teacher included average increases by 1 kg means the teacher gives 1 kg to every student
Total he gives = 25 × 1 = 25 kg
Now teacher’s weight = 51 kg
Therefore, actual weight of teacher = 25 51 = 76 kg
2. The average age of 11 students in a class and the class teacher is 18 years. If the age of the teacher is not considered, then the average decreases by 1 year. Find out the age of the teacher.
a) 28 years b) 29 years c) 30 years d) 31 years
Ans: b
Solution: 11 teacher
Average = 18 years
Average = 17 years
When the teacher age is not considered average = 17
That means teacher takes 1 year from each student
Total = 11 × 1 = 11 years
Teacher age = 18 11 = 29 years
3. The average age of students of a school is 15 years. 10 students of average age 12 years join the school and the average age of a student of the school becomes 14.8 years. The original strength of the school was?
a) 120 b) 80 c) 140 d) 60
Ans: c
Solution: Students Average
x ->; 15
x 10 ->; 14.8
15x 10 × 12 = (x 10) × 14.8
0.2x = 28 =>; x = 140
4. Average weight of 35 students in a class is 40 years. 5 of the students of this class, whose average weight is 42 kg, left the class. Find the average weight of the remaining 30 students.
a) 39 kg b) 39 kg c) 39 kg d) None
Ans: c
Solution: Difference = 42 – 40 = 2 kg
2 × 5 = 10kgs
10/30 = 1/3
Therefore, 40 – 1/3
39 1 – 1/3
39 (2/3)
