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⁞ Averages

Aptitude ➤ Averages ➤ 1

Average:
Average = Sum of observations / Number of observations

Average Speed :
Suppose a man covers a certain distance at x kmph and an equal distance at y kmph.
Then, the average speed druing the whole journey is [2xy/(x+y)] kmph.

Question 1
Q1.  The average of four consecutive even numbers is 27. Find the largest of these numbers ?
 

Answer :  30


Let the numbers be x, x+2, x+4 and x+6.
Then,
(x+(x+2)+(x+4)+(x+6))/4 = 27
⇒ (4x+12)/4 = 27
⇒ x+3 = 27
⇒ x = 24.
Therefore the largest number = (x+6) = 24+6 = 30.
⚔ DISCUSS

Question 2
Q2.  The average of 20 numbers is zero. Of them, at the most, how many may be greater than zero ?
 

Answer :  19


Average of 20 numbers = 0.
∴ Sum of 20 numbers (0 x 20) = 0.
It is quite possible that 19 of these numbers may be positive and if their sum is (a) then 20th number is (-a).
⚔ DISCUSS

Question 3
Q3.  Average age of boys in a class is 16 years and average age of girls is 15 years, what is the average age of all ?
 

Answer :  Can't be computed


As number of girls and boys is not given so result cant be computed.
⚔ DISCUSS

Question 4
Q4.  There are two sections A and B of a class consisting of 36 and 44 students respectively. If the average weight of section A is 40 kg and that of section B is 35 kg, Find the average weight of the whole class ?
 

Answer :  37.25 Kg


Total weight of (36 + 44) students = (36x40 + 44x35) kg = 2980 kg.
Therefore, weight of the whole class = (2980/80) kg = 37.25 kg.
⚔ DISCUSS

Question 5
Q5.  The average of 25 results is 18. The average of 1st 12 of them is 14 and that of last 12 is 17. Find the 13th result.
 

Answer :  78


Clearly, 13th result = (sum of 25 results) - (sum of 24 results)
= (18x25) - [(14x12)+(17x12)]
= 450 - (168+204)
= 450 - 372
= 78.
⚔ DISCUSS

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