In a group of 40 people, if two people, Tom and Jerry, swap their ranks and Tom is initially 10th from the top and Jerry is 20th from the bottom, what will be Tom's new rank from the bottom after the swap?
Answer: B. 30th
After the swap, Tom's new rank from the bottom is 40 - 10 + 1 = 31, but since Jerry was 20th from the bottom, Tom takes that rank, which is 20th from the bottom.