Aptitude - Average - Discussion

@Naveen.

Total number of students = 120,
Let X be the number of passed candidates then 120-X is the number of failed candidates.
Average marks of 120 students = 35,
Average of passed candidates =39,
Average of failed candidates =15,

Therefore,
Total marks of 120 students = 35*120 = 4200,
Total marks of passed candidates= 39 * X,
Total marks of failed candidates = 15 *(120 - X) = 1800 -15 X,
Total marks of passed candidates + Total marks of failed candidates = Total marks of 120 sudents.

ie 39X + 1800 - 15X = 4200,
39X - 15X = 4200 - 1800,
24X = 2400,
X = 100,
ie The number of passed candidtes = 100 (Answer).

The average of six consecutive integers in increasing order size is 9.5. What is the average of the last three numbers?

Can anyone solve this?

@Niraj.

The answer is 46.

The average weight of three men 'X', 'Y' and 'Z' is 75 kgs. Another man 'A' joins
the group and the average weight now becomes 80 kgs. If another person 'B' whose
weight is 5 kgs more than 'A' replaces 'X', then the average weight of 'Y', 'Z', 'A' and
'B' will be 85 kgs. What is the weight of 'X'?

Can anyone solve this?

Thanks @Bhanu.

Your method is good, Thanks @Bhanu.

Thanks @Anonymous.

Let the average weight of 8 persons be x and the weight of first 7 persons be A.

The weight of 8 persons is A+ 65 = 8x ---> (1)
After replacing the person having weight 65, the average weight of 8 persons increased by 2.5
Now the average weight of 8 persons will be 8(x+2.5) and;

The weight of 8 persons will be A + Z(replaced person weighing 65) = 8(x+2.5) ---> (2)
Subtract (1) from (2) i.e.,
A+Z-(A+65) = 8(x+2.5) - 8x,
A+Z-A-65 = 8x + 20 -8x,
Z-65 = 20,
Z = 20+65,
Z = 85 Weight of replaced person.

Thanks for the answer. @Bhanu.

Total weight of 8 persons is 520 (65*8).
Now, a total weight of 7 persons is 455 (520-65),
Now try every option to get 2.5% increase,
(455+85)/8 is equal to 67.5,
The total increase is 2.5 KG (67.5-65),
Ans is 85 KG.