Aptitude - Average - Discussion

Let x be an average of 8 persons.
Let y be the weight of the new person.
(x+y-65)/8 = (x/8)+2.5,
x+y-65 = x+20,
y-65 = 20,
y = 85.

By using formula,
a = r+nx ------>
a = Added value.
r = Removed value.
n = Number of persons.
x = Change in avg.

So,
a = 65+8(2.5).
a = 85 is new person weight.

Let the average was 10.

Then the sum of 8 people was 10*8 = 80.
When new person comes ,average was increased by 2.5 so new average is 12.5 the new sum = 12.5 * 8 = 100.

So the difference is of 20.
Now whoever new person he will increase the sum by 20 so new person weight is 65 + 20 =85 is the Answer.

Can you guys tell me about what happens if the weight is decreased by 2.5 kg? Please explain.

Not able to understand.

Here you poised 20kg to this person's weight but not well 20kg should be added to all persons in one person's weight only 2.5kg should be added.

Am I right.

@Tinku.

Thanks for your explanation.

@Manoj Kumar.

Thanks for explaining. Your method is very helpful to solve the QA questions.

Simple formula.

Weight Of replcae +- (increase/decrease)* number.

2.5 = 2 + 1/2 = 5/2
8 × 5/2 = 20,
65 + 20 = 85.

Age of captain = 26 ...
So the age of the wicket-keeper who is 3 years older than the captain = 29
Let avg of 11 members be x, then
The sum of observations /11 = x.

I. e 26+29+ remaining sum of 9 members = 11x.
Remaining sum of 9 = 11x-55--->(1)
Given that, avg of the remaining 9 will be one less than the total average.
So total avg is x, then the of 9 is x-1.

I. e sum of remaining 9/9 = x-1.
Sum of remaining 9 = 9x-9 ----> (2)
9x-9 = 11x-55 from 1 and 2.

11x -9x = -9+55.
2x = 46,
x= 46/2 = 23.