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?

K+L+M = 72 (average 24 × 3). When N joins: K+L+M+N = 92 (average 23 × 4), so N = 92-72 = 20. R is 2 years older than N, so R = 22. When R replaces K: L+M+N+R = 90 (average 22.5 × 4). Since L+M+N = 72-K and R = 22, we have (72-K)+22 = 90, so 94-K = 90, giving K = 4. But this doesn't match option D (24). Let me recalculate: K+L+M = 72. K+L+M+N = 92, so N = 20. L+M+N+R = 90 (when R replaces K). But L+M = 72-K, and N = 20, R = 22. So (72-K)+20+22 = 90, which gives 114-K = 90, so K = 24.