In a hostel 30% of the residents are vegetarian. If 20 more residents join and every one of them is vegetarian, vegetarians become 40% of the hostel. The number of residents before the 20 joined was:

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Accepted Answer

120. With n residents to start with, (0.3n + 20)/(n + 20) = 0.4 gives 0.3n + 20 = 0.4n + 8, so n = 120 (36 vegetarians, then 56 out of 140 = 40%). 140 is the hostel AFTER the newcomers, and treating the 10-point rise in the share as though the 20 newcomers were 10% of the original strength gives 200.

In a hostel 30% of the residents are vegetarian. If 20 more residents join and every one of them is vegetarian, vegetarians become 40% of the hostel. The number of residents before the 20 joined was:

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