Aptitude preparation
Aptitude on average
Aptitude questions and answers on average


1. Find the Average of first 50 naturals numbers ? 

Correct Answer:Option
B
Explanation:
Sum of first n natural numbers = n(n+1)/2.
So (50*51)/2 =1275 , There fore Required average = 1275/50 = 25.5
2. Find the Average of prime numbers between 10 to 20 ? 

Correct Answer:Option
C
Explanation:
Prime numbers between 10 to 20 are 11 , 13 , 17 , 19 .
(11+13+17+19) / 4 = 15.
3. What is the Average of first five multiple of 2 ? 

Correct Answer:Option
B
Explanation:
2(1+2+3+4+5) / 5 = 6
4. There are 40 students in aclass. The average age of 10 students is 15 years.The average age of next 30 students is 12.5 years.What is the average age of whole class ? 

Correct Answer:Option
A
Explanation:
Total age of 10 students =15 *10 = 150
Total age of 30 students = 12.5 * 30= 375
Average age of 40 students = 150+375 / 40 = 525/40 = 13.1
5. 20 pens and 55 pencils were purchased for Rs.600.If the average price of a pencil was Rs.2 , find the average price of a pen ? 

Correct Answer:Option
D
Explanation:
Since average price of a pencil = Rs. 2
Therefore Price of 55 pencils = Rs.110 , Price of 20 pens =600110 = 490
average price of a pen = 490/20 =24.5
6. If the number of quantities is 12 and their sum is 540, then their average is ? 

Correct Answer:Option
B
Explanation:
Let the number of quantities be N and their sum is S then Average = S/N.
So Average = 540/12 = 45.
7. If the number of quantities is 10 and their average is 56 .Find the sum of quantities ? 

Correct Answer:Option
C
Explanation:
Let the number of quantities be N and their Average be A .
Average = Sum of quantities / Number of quantities > Sum of quantities = Average * Number of quantities . i.e., S = A * N
So 56 * 10 = 560
8. The average of 6 quantities is 10 , the average of 3 of them is 8. Find the average of remaining quantities ? 

Correct Answer:Option
A
Explanation:
(6*10 +3*8) / 108 = 18 .
average of X quantities is P.and the average of Y of them is Q then the of average remaining quantities Formula: Remaining average = PX  QY / P  Q.
9. If the average is 35, and their sum is 700 then find the number of quantities ? 

Correct Answer:Option
B
Explanation:
Average = sum of quantities / number of quantities > number of quantities = sum of quantities / Average.
So number of quantities = 700 / 35 = 20
10. To find the geometic mean (GM) of 2 , 3 , 4 and 5 ? 

Correct Answer:Option
B
Explanation:
geometric mean (GM) of N quantities = Nth root ( x1*x2*x3.......)
So 4th root (2*3*4*5) = 4th root (120) = 30
11. If the marks obtained by Rajesh in maths, science and social are 67 , 72 and 80 respectively ,then his average score is ? 

Correct Answer:Option
A
Explanation:
Average marks = (67 + 72 + 80) / 3 = 219/3 = 73.
12. A man walks 2500 metres in 40 minutes , 1000 metres in 30 minutes and 500 metres in 10 minutes. Then what is the average speed for whole walking distance ? 

Correct Answer:Option
B
Explanation:
Average marks = (2500+1000+500) / (40+30+10) = 4000 / 80 = 50
13. The average of 35 numbers is zero.Of them, at the most ,how many may be greater than zero ? 

Correct Answer:Option
C
Explanation:
Average of 35 numbers = 0 , therefore sum of 35 numbers = 0 * 35 =0.
It is possible that 34 of these numbers may be positive and if there sum is x , then the 35th number is x.
14. Find the average of all the numbers between 5 to 25 , which are divisible by 3 ? 

Correct Answer:Option
C
Explanation:
Average = ( 6+9+12+15+18+21+24) / 7 = 105 / 7 =15.
15. Find the arithmetic mean of 3 , 5 , 7 , 8 , 13 , 17 ,22 and x. Mean is 10 ,what should be the number in place of x ? 

Correct Answer:Option
A
Explanation:
Mean or average = (3+5+7+8+13+17+22+x) / 8 =10 > (75 +x) /8 =10 > x = 80 75 = 5.
16. If the average of 4 observations x, x+2 , x+4 , x+6 is 20 , find the average of last two observations ? 

Correct Answer:Option
A
Explanation:
Mean or average of given observations is 20 . i.e., (x+x+2 + x+4 + x+6 ) / 4 = 20 > 4x +12 =80 >4x = 8012 = 68 > x = 68/4 = 17.
x = 17 then average of last two observations is x+4 = 17+4 = 21 , x+ 6 = 17 +6 = 23 , average = 21+23/2 =44/2 = 22.
17. Suresh average daily expenditure is Rs.16 during march , Rs.12 during april , Rs.22 during may.What is the average daily expenditure for the three months ? 
A.

Rs.18 approx 
B.

Rs.14.5 approx 
C.

Rs.17 approx 
D.

None of these 

Correct Answer:Option
C
Explanation:
average daily expenditure = ((16*31)+(12*30)+(22*31)) / 31+30+31 = (496+360+682) / 92 = 1538/92 = 16.7 = 17 Approx.
18. Find the average of squares of consecutive odd numbers till 9 ? 

Correct Answer:Option
D
Explanation:
9(9+1) / 3 = 9*10 / 3 = 90/3 =30.
Average of squares of consecutive odd numbers till N = N(N+1) / 3.
19. Find the average of squares of consecutive even numbers till 13? 

Correct Answer:Option
A
Explanation:
(13+1)(13+2) / 3 = 14*15 / 3 = 210/3 =70.
Average of squares of consecutive even numbers till N = (N+1)(N+2) / 3.
20. What would be the average of cubes of consecutive 15 natural numbers ? 

Correct Answer:Option
D
Explanation:
15(15+1)² /4 = 15*(16)² /4 = 15 * 256 /4 = 3840/4 = 960.
average of cubes of consecutive n natural numbers = N(N+1)² /4 .
21. Find the average of consecutive 25 natural numbers ? 

Correct Answer:Option
C
Explanation:
(25+1) / 2 = 26/2 = 13
Average of consecutive n natural numbers = (n+1)/2
22. What is the average of square of consecutive 5 natural numbers ? 

Correct Answer:Option
A
Explanation:
(5+1) ((5*2) +1) / 6 = 6 * 11 /6 = 66/6 = 11
Average of square of consecutive n natural numbers = (n+1) (2n+1) / 6.
23. Find the average of cubes of consecutive 10 natural numbers ? 

Correct Answer:Option
B
Explanation:
10(10+1)² / 4 = (110)²/4 = 12100 /4 = 3025
Average of cubes of consecutive n natural numbers= n(n+1)² / 4.
24. What would be the average of 22 consecutive even numbers ? 

Correct Answer:Option
C
Explanation:
22+1 = 23
Average of n consecutive even numbers = n+1.
25. The average of 6 numbers is 32, if one number is exclude the average becomes 27. what is the exclude number ? 

Correct Answer:Option
C
Explanation:
Let the excluding number = (6*32)  (5*27 ) = 192  135 = 57.
Average = sum of quantities / number of quantities
sum of quantities = number of quantities * Average. If we want to find the excluding number then we have to subtact .
26. The average marks of 11 students is 54, the first five students is 20 and that of the last five students is 28. Find the value of 6th number ? 

Correct Answer:Option
B
Explanation:
6th student marks number = Total of 11 students result – ( Total of first five students + Total of last five students results ).
6th student marks number = 11*54  (5*20 + 5*28)
> 594  (100+140)
594240 = 354.
27. Anil travels to a place 200 km away at an average speed of 70 km/hr and returns at 32 km/hr. Find the average speed for whole journey in km/hr ? 

Correct Answer:Option
C
Explanation:
Average speed = 2xy/ x+y .
Average speed of given problem = (2*70*32) / 70+32
(140 *32) /102 = 4480/102 = 43.92
Average speed of given problem =43.92.
28. If a cyclist cycles a distance at the speed of 15 km/hr and comes back at a speed of 35 km/hr, then find his average speed ? 

Correct Answer:Option
B
Explanation:
(2*15*35) / (15+35) = 1050 / 50 =21 km/hr.
Formula: Average speed =( 2xy / x+y) km/hour.
General average speed = Total distance travelled / Total time taken. In this case distance travelled would be double.
29. Find the sum of consecutive odd number in a group 1 to 60 ? 

Correct Answer:Option
A
Explanation:
we know that the odd numbers exists in between 1 to 60 is 30.
30 x 30 = 900.
Rules : we just follow the rule like n x n = result, Square the quantity of numbers in the series.
30. If the average weight of 6 men increases by 4 kg when one of them weighing 80 kg is replaced by another man. Then find weight of the new man ? 

Correct Answer:Option
C
Explanation:
Answer : 80+(3*4) = 104.
Formula : Measure of new quantity = Measure of removed quantity + (change in average * number of quantities).
Change could be +ve or ve.
31. If the average weight of 15 men is 60kg,and that of 20 women is 50kg,Then find the average weight of 35 persons ? 
A.

54 
B.

54 2/7 
C.

56 3/4 
D.

None of these 

Correct Answer:Option
B
Explanation:
average weight of 35 persons = ((15*60) + (20*50)) / 35 > (900+1000) / 35 = 1900/35 = 54 2/7.
To find the average of x+y quantities, if the average of x quantities is 'a' and the average of y quantities is 'b',Then
Formula: Average = (xa+yb) / x+y.
32. The average of 13 results is 68.The average of first seven is 63 and that of last seven is 70.Then find the seventh result ?


Correct Answer:Option
A
Explanation:
(63+70)7  (13*68) = 47.
To find the measure of the y th quantity,the total quantities being 2y1=n, given that the average of 1st y quantities is 'a' and of the last y quantities is 'b' and the combined average of n (=2y1 ) quantities is x.
Formula: (a+b)y  nx
33. What fraction must be subtracted from the sum of 1/2 and 1/6 so that the average of the three may become 1/15 ? 

Correct Answer:Option
B
Explanation:
Required fraction = (the sum of three fraction)  (1/2+1/6)
= (3*1/15)  4/6
= (1/5)  (4/6)
= (820)/30
= 2/5.
34. Find the average of consecutive natural numbers from 20 to 80 ? 

Correct Answer:Option
C
Explanation:
Average = (1st number + last number) / 2.
So Average of given numbers = (20+80) / 2 =100/2 =50.
35. Find the average of consecutive even numbers to 80 ? 

Correct Answer:Option
A
Explanation:
Average = ((N/2)+1)
=(80/2)+1 = 40+1 = 41.
36. The average temperature of first four days of a week is 38°C and the average temperature of last four days is 45°C but the average temperature of that week is 42°C,Find the temperature of the fourth day of that week ? 

Correct Answer:Option
B
Explanation:
The temparature of the fourth day = (Total temparature of the first four days ) + ( Total temparature of the last four days)  (Total temparature of that week)
= 4 * 38°C +4 *45°C  7 *42°C
= 4(38°C + 45°C)  294°C
= 332°C  294°C
= 38°C
37. The average score of cricketer in 4 matches is 30 and in 8 others in 15.Then find his average score in 6 matches ? 

Correct Answer:Option
B
Explanation:
Average score = (4 *30)+(8 * 15) / 8+4
= (120+120) /12
= 240/12 =20.
38. What is the average of 10 , 20 , 30 , 40 ,50 ? 

Correct Answer:Option
A
Explanation:
Average = (10+20+30+40+50) / 5
Average = 150 / 5 = 30
39. The average salary of 25 workers in an office is Rs.3000 per month.If the manager's salary is added,the average salary becomes Rs.3200 p.m.What is the manager's salary ? 

Correct Answer:Option
B
Explanation:
Salary of the manager = Average salary of 25 workers + (25+1) * increasement in average salary.
3000+26*200 = 3000 + 5200 = 8200.
40. Find the mean of 2 ,3 , 4 ,5 ,6 ? 

Correct Answer:Option
A
Explanation:
Average = 2+3+4+5+6 / 5 = 20/5= 4.
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