百分數應用題唔識做啊~!HELP~

1)10x(100%+15%)x10x(100+15%) - 10x10
---------------------------------------------------------- x100%
10x10

=11.5x11.5 - 10x10
--------------------------- x100%
10x10

=132.25-100
----------------x100%
100

=32.25%



2)設正方體的邊長為10cm,
新正方體的邊長=10x(100%-10%) x 10x(100%-10%) x 10x(100%-10%)
=9x9x9
=729cm^3
舊正方體的邊長=10x10x10
=1000cm^3
正方體體積的百分減少.=1000-729
-------------x100%
1000

=27.1%


3) 120000
--------------------
100% - 25%

=120000
-----------
75%

=$160000






攔我啦!我好俾心機做的!

2007-12-16 23:21:03 補充：
2)設正方體的邊長為10cm,新正方體的邊長=10x(100%-10%) x 10x(100%-10%) x 10x(100%-10%)=9x9x9=729cm^3舊正方體的邊長=10x10x10=1000cm^3正方體體積的百分減少.=1000-729 -------------x100% 1000=27.1%要吞過少少位,i'm sorry.

1)The new aera is
10x(1+15%)x10x(1+15%)
=132.25
The percentage of the aera increase
32.25
-----------x100%
100
=32.25%(1d.p.)
2)Let100be the orinigal area.
10x10-9x9
--------------x100%
10x10
=19%
3)
120000/(1-25%)
=$160000

Check it by yourself again!!!Must!!!

1)若邊長10cm的正方形的各邊增長15%,求正方形的面積的百分增加.
已知邊長為10cm
舊正方形的面積 = 10*10 = 100 cm^2
各邊增長15%
新邊長 = 10 * (100% + 15%) = 11.5cm
新正方形的面積 = 11.5*11.5 = 132.25 cm^2
百份比改變 = (新 - 舊)/(舊) * 100% = (132.25 - 100)/100 * 100% = 32.25% 即 正方形的面積增加了 32.25%

2)一個正方體的邊長減少了10%,求正方體體積的百分減少.
假設邊長為 x
正方體體積 = x*x*x = x^3
各邊長減少10%
新邊長 = x * (100% - 10%) = 0.9x
新正方體體積 = (0.9x)*(0.9x)*(0.9x) = 0.729x^3
百份比改變 = (新 - 舊)/(舊) * 100% = (0.729x^3 - x^3)/(x^3) * 100% = -27.1%
即 正方體的體積 減少了 27.1%

3)某東西以120 000售出,虧蝕25%,求某東西的成本.
假設原來既售價 (成本) 為 x
百份比改變 = (新 - 舊)/(舊) * 100% = (120000 - x)/x = -25%
so, 120000 - x = (-1/4)*x
480000 - 4x = -x
3x = 480000
x = 160000
所以成本為 160 000

希望幫到你

2007-12-18 09:10:36 補充：
第2題果度
設正方體的邊長為10cm
唔太應該係條式度出現..
如果做多項選擇題既時候就冇乜所謂
但係答緊問題就好似唔係咁好

感覺上...設為x 會合理d

i) (115%*115%/100%*100%)*100%
=(13225%/10000%)*100%
=32.25%
ii) [(100%*100%*100%-10%*10%*10%)/100%*100%*100%]*100%
=(1-0.729)/1
=0.271
=27.1%
iii)120000/(1-25%)
=120000*4/3
=160000

1) Let the side of the square be x
if the side increase by 15% it becomes 1.15x

the original area = x^2
the new area =(1,15x)^2 = 1.3225x^2

increase in area = 1.3225x^2 - x^2 = 0.3225x^2
area increase in % = 0.3225x^2/x^2 = 0.3225 = 32.25%

2) Let the side of the cube be x
if the side decrease by 10% it becomes 0.9x

the original volume = x^3
the new volume =(0.9x)^3 = 0.729x^3

decrease in volume = x^3 - 0.729x^3 = 0.271x^3
decrease in % = (0.271x^3)/x^3 = 0.271 = 27.1%

3) Cost = 120 000/(1-25%) = 160 000