For the past n days, the average (arithmetic mean) daily production at a company was 50 units. Iftoday's production of 90 units raises the average to 55 units per day, what is the value of n ?
(A) 30
(B) 18
(C) 10
(D) 9
(E) 7
答案：E
If a two-digit positive integer has its digits reversed, the resulting integer differs from the original by 27.By how much do the two digits differ?
(A) 3
(B) 4
(C) 5
(D) 6
(E) 7
答案：A
答案：E
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