Quantitative Aptitude

Averages

1,527 Questions
All Basic average and reverse calculation 405 Adding or removing an observation 342 Weighted and combined averages 320 Replacement and correction of a recorded value 233 Ratio shortcut for two-group mixtures 111 Equal-distance average speed 59 Age, score, weight, and spending applications 32 Consecutive terms and arithmetic progressions 25

Averages Questions

Multiple choice

There were 24 students in a class. One of them who was 18 year old left the class and a new student joined and the average age of class reduced by 1 month. Find the age of newcomer.

  1. 14 years

  2. 15years

  3. 16 years

  4. 17 years
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Total age change = (number of students) * (change in average). The average reduced by 1 month (1/12 year). Total change = 24 * (-1/12) = -2 years. The new student is 2 years younger than the one who left. Age = 18 - 2 = 16.

Multiple choice

A girl finds the average of 6 positive integers, each integers containing two digits. By mistake she interchanges the digit of one number say xy for yx. Due to this the average becomes 1.5 less than the previous one. What was the difference between two digits x and y.

  1. 1

  2. 2

  3. 3

  4. 4

  5. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the number be 10x + y. Interchanging gives 10y + x. The difference in the number is 9(x-y). The average change is 1.5, so the total sum change is 1.5 * 6 = 9. Thus, 9(x-y) = 9, meaning x-y = 1.

Multiple choice

There are three numbers. If 3rd number is 50% more than that of 1st number and 25% more than that of 2nd number then find out the average of all three numbers (given that smallest number = 30)

  1. 37

  2. 40

  3. 35

  4. 38

  5. 42
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Smallest number = 30. If 3rd is 50% more than 1st, 3rd = 1.5 * 1st. If 3rd is 25% more than 2nd, 3rd = 1.25 * 2nd. If 1st = 30, 3rd = 45. Then 45 = 1.25 * 2nd, so 2nd = 36. Average = (30 + 36 + 45) / 3 = 111 / 3 = 37.