请教 3道题的解题方法 非常感谢

mataoturku

On a purchase of $120, a store offered a
payment plan consisting of a $20 down
payment and 12 monthly payments of
$10 each. What percent of the purchase
price, to the nearest tenth of a percent,
did the customer pay in interest by
using this plan?

The sum of the interior angles of any
polygon with n sides is 180(n – 2)
degrees. If the sum of the interior
angles of polygon P is three times the
sum of the interior angles of
quadrilateral Q, how many sides does
P have?

If an organization were to sell n
tickets for a theater production, the
total revenue from ticket sales would
be 20 percent greater than the total
costs of the production. If the
organization actually sold all but 5
percent of the n tickets, the total
revenue from ticket sales was what
percent greater than the total costs of
the production?

非常感谢

royalex

第一题没看明白，555，是不是20/120？

第二题，设P有X条边，那么180(X-2)=3*180*(4-2)，解X=8

第三题，n张票全卖光是120%的cost，卖了95%的票，那么就是120%*95%的cost，1.2*0.95-1=0.14，所以是14%

[此贴子已经被作者于2009-6-20 6:57:25编辑过]

mataoturku

第一题，我也看不明白

第二题，能不能帮我翻译一下

xiexie