Q. A bag contains 5 red balls and 3 blue balls. If the average weight of the red balls is 200 grams and the blue balls is 150 grams, what is the average weight of all the balls?
A.175
B.180
C.185
D.190
Solution
Total weight of red balls = 5 * 200 = 1000 grams. Total weight of blue balls = 3 * 150 = 450 grams. Total weight = 1000 + 450 = 1450 grams. Average weight = 1450 / 8 = 181.25.
Q. A class has 30 students. If the average score of the class is 75 and one student scored 90, what will be the new average if that student is removed?
A.74
B.75
C.76
D.77
Solution
Total score = 30 * 75 = 2250. New total = 2250 - 90 = 2160. New average = 2160 / 29 = 74.48, approximately 74.
Q. A class has 30 students. If the average score of the class is 75 and one student scored 90, what is the average score of the remaining students?
A.72
B.74
C.76
D.78
Solution
Total score of 30 students = 30 * 75 = 2250. Total score of remaining 29 students = 2250 - 90 = 2160. Average of remaining = 2160 / 29 = 74.48, approximately 74.
Q. A class of 30 students has an average score of 75. If a new student joins and the average becomes 76, what is the score of the new student?
A.80
B.85
C.90
D.95
Solution
The total score of 30 students is 30 * 75 = 2250. After the new student joins, the total score becomes 31 * 76 = 2356. Therefore, the new student's score is 2356 - 2250 = 106.
Q. A family has 4 members with an average age of 25 years. If the youngest member is 10 years old, what will be the average age if the youngest member turns 20?
A.26
B.27
C.28
D.29
Solution
Total age of family = 4 * 25 = 100. New total age after youngest turns 20 = 100 - 10 + 20 = 110. New average = 110 / 4 = 27.5, approximately 27.
Q. A group of 6 people has an average weight of 70 kg. If one person weighing 80 kg leaves, what is the new average weight?
A.68
B.69
C.70
D.71
Solution
The total weight of the group is 6 * 70 = 420 kg. After the 80 kg person leaves, the total weight becomes 420 - 80 = 340 kg. The new average is 340 / 5 = 68 kg.
Q. In a group of 10 people, the average age is 30 years. If two new members join the group and the average age becomes 32 years, what is the average age of the new members?
A.34
B.36
C.38
D.40
Solution
Total age of 10 people = 10 * 30 = 300. New total age = 12 * 32 = 384. Age of new members = 384 - 300 = 84. Average age of new members = 84 / 2 = 42.
Q. In a group of 5 friends, the average age is 24 years. If the age of one friend is 30 years, what is the average age of the remaining friends?
A.22
B.23
C.24
D.25
Solution
The total age of the 5 friends is 5 * 24 = 120. The total age of the remaining 4 friends is 120 - 30 = 90. The average age of the remaining friends is 90 / 4 = 22.5.
Q. In a group of 6 friends, the average age is 22 years. If one friend leaves and the average age becomes 23 years, what is the age of the friend who left?
A.20
B.22
C.24
D.26
Solution
Total age of 6 friends = 6 * 22 = 132. Total age of 5 friends = 5 * 23 = 115. Age of friend who left = 132 - 115 = 17.
Q. In a race, the average speed of a runner is 10 km/h. If he runs for 2 hours and then increases his speed to 15 km/h for the next 3 hours, what is his average speed for the entire race?
A.12
B.13
C.14
D.15
Solution
Total distance = (10 * 2) + (15 * 3) = 20 + 45 = 65 km. Total time = 2 + 3 = 5 hours. Average speed = 65 / 5 = 13 km/h.
Q. The average age of a group of 10 people is 30 years. If two new members join the group, increasing the average age to 32 years, what is the average age of the new members?
A.36
B.38
C.40
D.42
Solution
Total age of 10 people = 10 * 30 = 300. New total age = 12 * 32 = 384. Age of new members = 384 - 300 = 84. Average age of new members = 84 / 2 = 42.
