The average weight of 20 persons sitting in a boat had some value. A new person added to them whose weight was 47 kg only. Due to his arrival, the average weight of all the persons decreased by 5 kg. Find the average weight of first 20 persons? Choose the correct choice:
A) 55
B) 56
C) 57
D) 58
E) 59

Rationale: "20 x + 47 = 21 ( x – 5 ) x = 58 answer : d"
Answer: D