F.1 Maths

1.In a plan, 4% of the seats are first class, 16% are business class and the rest are economy class. There are 240 economy class seats.If 20 economy class seats are removed, what percentage of the seats are first class?
the total number of the seats=240/(1-4%-16%)=240/0.8=300
the percentage of the seats are first class
=[300(4%)/300-20]*100%
=4.29% (corr. to 3 sig. fig.)

2.Tom buys 500 TV game sets at a total cost of $100000. If each game set is sold at a discount of 20% and he makes a profit of 20%, find

(a) his total profit,

=100000(20%)
=$20000

(b)the selling price of each game set,
Let the the selling price of each game set be $x
x-100000=20000
x=120000
Therefore,the the selling price of each game set is $120000

(c)the marked price of each game set.
=120000/(1-20%)
=120000/0.8
=$150000


2008-02-04 23:53:37 補充：
Sorry for typing mistake.2(b)the the selling price of each game set =120000/500=$2402(c)the marked price of each game set=150000/500=$300

2008-02-06 17:48:57 補充：
其實4又7分之2%即係4.29%,你試下禁下機數機4又7分之2=30/7=4.29(準至3位有效數字)

1. Firstly, we know that 240 economy class seats (80%), 12 first class (4%) and 48 business class (16%), total = 300 seats.

Then, if 20 economy class seats are removed, then it becomes 280 seats.
The percentage of the first class is 4/280 = 1.428571%

2. a. The profit is still 20%, i.e., $100000*20% = $20000
b. The selling price of each game = $120000/500 = $240.
c. The marked price of each game (before 20% discount) = $240/0.8 = $300.