A group of three friends K L and M are sitting in a cafe Their average age is 24 years Another frien...........

Quantitative Aptitude (CGL) Problems based on Ages

A group of three friends, K, L and M, are sitting in a cafe. Their average age is 24 years. Another friend ‘N’ joins the group and the new average age of the group becomes 23 years. If another friend ‘R’, whose age is 2 years more than that of ‘N’, replaces ‘K’, then the average age of L. M, N and R becomes 22.5 years. What is the age of K?

This questions was previously asked in

SSC CGL 6th March 2020 Shift-2

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15 years

10 years

12 years

24 years

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Explanation:

Correct option 4: 24 years

According to the given information,
Average of K, L and M is 24
K+L+M/3 = 24
K+L+ M = 72 ...1)
Average of K, L, M and N is 23
K+L+M+N/4 = 23
K+L+M+ N = 92 ...2)
Substituting (1) in (2)
72+ N = 92
N = 20
R who is two years older than N replace K
R = 22
Average of R, L, M and N is 22.5
R+L+M+N/4 = 22.5
R+L+M+N = 90
22 +L+M+20=90
L+ M = 48
Substituting this in (1)
K + 48 = 72
K = 24
K is 24 years old.