[個人分享]有題數唔識做，教下我可以嗎？加多part c [複製鏈接]

Mr . Tsang is going to hold two talks at The Hong Kong Exhitbition Centre.Suppose the theatre can accommodateat most 8 000 people. He estimates that if the price for each ticket is $50, then 80% of the tickets will be sold.For every increase of $0.5 in the ticket price, the number of tickets sold will decrease by 25.

(a)Let $x be the price of each ticket and y be the number of the tickets sold.Express y in terms of x.

我think 唔到呀help!!!

yeah 計到啦
thank 咁多位
(c)Suppose the price of each ticket in the the second talk is $50, and he estimates 85% of the ticket will be sold . According to the condition stated above , find the maximum possible income in these two talks.

中幾的數來?
因為我有2個solution-.-
唔知比邊個你

引用第1樓202202於2010-12-28 14:58發表的  :
中幾的數來?
因為我有2個solution-.-
唔知比邊個你

我中4
最好比兩個我，我想學多d

小弟方法非常複雜

y=6000-25k (1)
x=50+0.5k (2)

from(1),
k=(6000-y)/25 (3)
from(2),
k=(x-50)/0.5 (4)

combine (3)&(4)
(6000-y)/25=(x-50)/0.5
6000-y=50x-2500

           y=8500-50x

有錯絕不負責(拖)

引用第3樓瑋哥於2010-12-28 17:24發表的  :
小弟方法非常複雜
y=6000-25k (1)
x=50+0.5k (2)
.......

你係唔係睇錯question 好似唔係6000係8000呀
仲有ans 係8900 -50x  
ya i got it

引用第4樓scfkipper於2010-12-28 17:27發表的 :
你係唔係睇錯question 好似唔係6000係8000呀

唔好意思
睇錯野
重做
y=6400-25k (1)
x=50+0.5k (2)

from(1), k=(6400-y)/25 (3)
from(2), k=(x-50)/0.5 (4)

combine (3)&(4)

(6400-y)/25=(x-50)/0.5
6400-y=50x-2500          
y=8900-50x

照舊，有錯不負責

income of the first talk=xy

x=50+0.5k
y=6400-25k
xy=320000+1950k-12.5k^2
   = -12.5(k^2-156k-25600)
   = -12.5( k^2-(2)(78)(k)+(78)^2 -(78)^2 - 25600 )
   = -12.5( (k-78)^2 - 31684 )
   = 396050 -12.5(k-78)^2

The maximum income of the first talk = 396050

For the second talk (步驟一樣不重復了，數字可能會有錯，請見諒orz)

x=50+0.5k
y=6800-25k
xy=340000+2150k-12.5k^2
   =340000 - 12.5 (k^2-172k)
   =340000 - 12.5(k-86)^2 +92450
   =452450 - 12.5(k-86)^2

The maxmum income of the second talk = 452450

ANSWER=452450+396050=$848500