數學問題(升中一)

方程:
1)Mr chan spends 1/4 of his income on rent and 1/6 on transportation.If the total
expenditure on rent and transportation is $7500,find Mr Chan's income.

Let $y be Mr Chan income.
y x 1/4 + y x 1/6 =7500
y/4 + y/6 =7500
12( y/4 + y/6 )=7500 x 12
3y + 2y =90000
5y =90000
5y/5 =90000/5
y =18000
.
. . Mr Chan income = $18000

百分數:
1)After Tina has eaten 23% of a box of candies,154 candies are left.

a)What percentage of the candies is left?

The percentage of the candies is left
= 1-23%
= 100% - 23%
= 77%

b)What is the original number of candies?

Let y be the original number of candies.
y x 77% =154
y =154 x 100/77
y =200
.
. .The original number of candies = 200

2)If we sell a wallet at 30% off,it is $72 cheaper than we sell it at 10% off.
What is the marked price of the wallet?

Let $y be the marked price of the wallet.
y[ ( 1- 10%) - ( 1- 30%)] =72
y[( 100% - 10%) - (100%- 30%)] =72
y( 90% - 70%) =72
y x 20% =72
y =72 x 100/20
y =360
.
. .The marked price of the wallet = $360

圖形:

1)The figure consists of a rectangle and a parallelogram.Find the area of the
shaded region.

無有圖,不能算。

2010-07-31 16:48:44 補充：
x 係乘

2010-08-01 12:47:05 補充：
.
. .係所以