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

Choose the correct answer from the alternative given. The average age of 15 students of a class is 15 years Out of these the average age of 5 students is 14 years and that of the other 9 students is 16 years. The age of the 15th student is:

  1. 11 years

  2. 4 years

  3. 15 years

  4. 14 years
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total age of 15 students = 15 * 15 = 225. Sum of 5 students = 5 * 14 = 70. Sum of 9 students = 9 * 16 = 144. Age of 15th student = 225 - (70 + 144) = 225 - 214 = 11.

Multiple choice

The average age of $r$ boys in a class is $a$ years. If the average age of $s$ of them is $b$ years, then what is the average age of the remaining boys ?
  1. $\displaystyle \frac{ra-sb}{r-s}$ years
  2. $\displaystyle \frac{ra+sb}{r-s}$ years
  3. $\displaystyle \frac{ra-sb}{r+s}$ years

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total age of r boys is r * a. Total age of s boys is s * b. The sum of ages of the remaining (r - s) boys is (r * a - s * b). The average age is (r * a - s * b) / (r - s).