EASY MATHS

1.Let Y be The cost price of 5 books;X be the selling price of 4 books
5X=4Y
(5/4)X=Y
Therefore, the gain percent of Tom is (120-100)%=20%
2.X be the origional prize;Y be the price of A sold to B
X(100-20%)=Y
Y(100-20%)=$40
Y=40/0.8
=50
X=50/0.8
=62.5

2006-12-11 18:09:31 補充：
Sorry.......Question 1 is wrong.......1.Let Y be The cost price of 5 books;X be the selling price of 4 books5X=4YX=(5/4)YTherefore, the gain percent of Tom is (125-100)%=25%

1. Let X = Cost price; Y = Selling price

Since the cost price of 5 books is the same as the selling price of 4 books,
5X=4Y
(5/4)X=Y
Selling price=Y=(5/4)X=1.25X

Gain percent=(125-100)%=25%

2. Let X = Original price of the drawing

Since A sold a drawing to B at a loss of 20%,
Selling price to B=X(100-20)%=0.8X

B sold it to C at a loss of 20%
Selling price to C=0.8X(100-20)%=0.64X

C used $40 to buy it
0.64X=40
X=62.5

A lost= $62.5-0.8*$62.5=$12.5