Aptitude - Average - Discussion

Let as assume A is average,
x is new person.
8A - 65 +x = 8*(A+2.5)
x = 85.

The new average is increased by 2.5, so we can say 8 * 2.5 = 20kg is the newly increased weight.

Such that the old person weight is 65 kg.

We have the newly added person weight, so 65 + 20 = 85 kg.

Average = Weights /number of members.

So,
Weights = Average * number of members.

If the Average increased by 2.5, then:
Weights will increase by (2.5 * 8) = 20.

Increase in weights = 20 kg,
The new person's weight = 65 + 20 = 85 kg.

Let's suppose Average age = 10
Age of sum of 8 ppl = 8×10 = 80
If age increases by 2.5 then = 12.5×8= 100,
Difference= 100-80 = 20.
New person age plus the difference of the ages of the first 8 ppl = 65+20,
= 85.

Here;
2 +1/2 Means 5/2.
a = 65+8* 5/2.
a = 85 is the new person's weight.

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.

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

Simple formula.

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

@Manoj Kumar.

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

@Tinku.

Thanks for your explanation.