CAT 2018 Question Paper | Quants Slot 1

CAT Questions

This is a super tricky question from Averages that appeared in CAT 2018 Question Paper. This question emphasizes the importance of Alligations way over Algebraic way that has to be practiced during your Online CAT Preparation . Do this wonderful question and see the video explanation from Rajesh.

Question 34 :In an apartment complex, the number of people aged 51 years and above is 30 and there are at most 39 people whose ages are below 51 years. The average age of all the people in the apartment complex is 38 years. What is the largest possible average age, in years, of the people whose ages are below 51 years? 

1. 25
2. 26
3. 27
4. 28

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Video Explanation

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Explanatory Answer

Method of solving this CAT Question from Averages

Given that the Average age of all the residents in the complex = 38 years
Number of people having ages 51 and above = 30
Number of people having ages below 51 ≤ 39
Since we need to maximize the average age of people below 51 and to maintain the combined average as 38 years, we need to consider the ages of people above 51 as 51 (Any more than that would lower the other value)
Also, We need to take the Number of people having ages below as 39 (Again, for maximizing the value)

So, 13 : 38-x = 39 : 30 = 13 : 10
38 - x = 10
x = 28
Average age of people whose ages are below 51 = 28 years

The question is "In an apartment complex, the number of people aged 51 years and above is 30 and there are at most 39 people whose ages are below 51 years. The average age of all the people in the apartment complex is 38 years. What is the largest possible average age, in years, of the people whose ages are below 51 years?"

Hence, the answer is 28 years

Choice D is the correct answer.