OG PS-Q108

[whyc0907]

108. Jan lives X floors above the ground floor of a high rise building. It takes her 30 seconds per floor to walk down the steps and 2 second per floor tp ride the elevator. If it takes Jan the same amount of time to walk down the steps to the ground floor as to wait for the elevator for 7 minutes and ride down, then X equals

(A) 4
(B) 7
(C) 14
(D) 15
(E) 16

我之前做這題沒有問題,今天有人問我這題把我問倒了
他的問題是:每層樓應該要減1,也就是說下X層樓走路時間應該是 30(X-1)
我自己的觀點是:題目已經說 30 second "per floor"
所以應該是 30X
雖然是很簡單的題目,各位大哥大姐可以給點意見嗎?

[chris8888]

假設 n floors
7 * 60 + 2 * n = 30 * n
n = 15