[問題] Form32 Sec6-Q15

[sam6521]

A certain theater has 100 balcony seats. For every ＄2 increase in the price of a balcony seat above ＄10, 5 fewer seats will be sold. If all the balcony seats are sold when the price of each seat is ＄10, which of the following could be the price of a balcony seat if the revenue from the sale of balcony seat is ＄1360?

(a)＄12
(b)＄14
(c)＄16
(d)＄17
(e)＄18

Ans:(c)

[Jacklin]

票價每多2元(10元以上)就少賣5個坐位，一個一個代，
12*95=1140
14*90=1260
16*85=1360
我試過列公式，但似乎沒有比較快，不知道有沒有數學高手能提供更快的方法!