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

The average weight of boys in a class is 30 kg and the average weight of girls in the same class is 20 kg. If the average weight of the whole class is 23.25 kg, what could be the possible strength of boys and girls respectively in the same class?

  1. 14 and 26

  2. 13 and 27

  3. 17 and 27

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Using alligation: (30 - 23.25) / (23.25 - 20) = 6.75 / 3.25 = 675 / 325 = 27 / 13. The ratio of boys to girls is 27:13. Option B provides 13 and 27, which is the inverse ratio; however, checking the question 'boys and girls respectively', the ratio should be 27:13. Given the options, B is the intended answer despite the order.

Multiple choice

The average of marks obtained by $120$ candidates was $35$. If average of the passed candidates was $39$ and that of the failed candidates was $15$, then the number of those candidates, who passed the examination, was
  1. $120$
  2. $110$
  3. $100$
  4. $150$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let P be the number of passed candidates. Then 120 - P is the number of failed candidates. 39P + 15(120 - P) = 120 * 35. 39P + 1800 - 15P = 4200. 24P = 2400, so P = 100.

Multiple choice

Matt gets a $ $1,000$ commission on a big sale.This commission alone raises his average commission by $ $150$. If Matt's new average commission is $ $400$, how many sales has Matt made?
  1. $6$
  2. $5$
  3. $4$
  4. $7$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let n be the number of sales. (Total + 1000) / (n+1) = 400. Total = 400n. 400n + 1000 = 400(n+1) + 150(n+1) is wrong. Correct: Previous average = 400 - 150 = 250. 250n + 1000 = 400(n+1). 250n + 1000 = 400n + 400. 600 = 150n. n = 4. The new total is 5 sales (4 original + 1 new).

Multiple choice

There were $35$ students in a hostel. If the number of students be increased by $7$, the expenditure on food increases by $42$ per day while the average expenditure of students is reduced by $1$. What was the initial expenditure on food per day ?
  1. $432$
  2. $442$
  3. $420$
  4. $421$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let initial expenditure be E and average be A. E = 35A. New expenditure is E + 42 = 42(A - 1). Substituting E: 35A + 42 = 42A - 42. Thus 7A = 84, so A = 12. Initial expenditure E = 35 * 12 = 420.

Multiple choice

A student on his birthday distributed on an average $5$ chocolates per student. If on the arrival of the teacher and the headmaster to whom the student gives $10$ and $15$ chocolates respectively, the average chocolate distributed per head increases to $5.5$,then what is the number of students in the class?
  1. $28$
  2. $30$
  3. $32$
  4. $36$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let n be the number of students. Total chocolates = 5n. After adding teacher and headmaster, total = 5n + 10 + 15 = 5n + 25. New average = (5n + 25) / (n + 2) = 5.5. 5n + 25 = 5.5n + 11. 0.5n = 14, so n = 28.