小六數學問題_很急//

1.
(10cm * 10cm * 1cm) / 4
= 2.5cm3

2.
(30cm * 30cm * 1cm) / (15cm * 10cm)
= 6cm

3.
(20cm * 20cm * 20cm) / 7500cm3
=500cm3

1.一個長10厘米,一個闊10,厘米高30厘米的長方體花瓶,盛裝了四分三的水。投入40粒大小相同的ball子後,水位上升了1厘米,每粒ball子的體積是多少立方厘米?
長方體花瓶的體積=10*10*30=3000cm2
上升水的體積=1*10*10=100
每粒ball子的體積=100/40=2.5

2.一塊長15cm,闊10cm的磚放入一個邊長是30cm的正方體水箱裡面,水位上升了0.01m這塊磚厚??
Let x be 這塊磚厚
15*10*x=30*30*0.05
150x=9
x=0.06

3.在一個邊長是20cm的正方體中放入一塊石頭後,再注入7.5升水,水箱剛好水。求石頭的體積。
注入7.5升水之前水的體積=20*20*20-7500
=500cm2
石頭的體積
=500cm2

I hope this can help you

1.每粒玻子的體積是:
10x10x1/40
=100/40
=2.5 (立方厘米)

2.這塊磚厚:
( 30 x 30 x 0.01x100)/(15 x 10 )
=( 30 x 30 x 1x100)/(15 x 10 )
=900/150
=6(cm)

3.體積是:
( 20 x 20 x 20 ) - 7500
=8000 - 7500
=500 ( 立方厘米 )

1. The height of the water in the vase is
30 x 3/4 = 22.5(cm) (since the base area is the same)
However it doesn't need to concern about the height of the water in this case
since
40 balls = the volume of the water that has been increased
= 10x10x1=100(cm3)
so a ball's volumn = 100 / 40 = 2.5cm3
Ans> The volumn of each ball is 2.5cm3

2. The volume of the brick = the volume of the water that has been increased
=30x30x0.01x100=900cm3 (Note, we have to change 0.01m into 1cm)
Let the thickness of the brick be d
then 15x15xd=900
d=4(cm)
Ans> The thickness of the brick is 4cm

3. First of all, we will need to find the height of the water, after it has been found
the rest height x base area = the volume of the stone

7.5L water = 7.5 x 1000 = 75000(cm3) = 75000ml
Let the height of water of 7.5L be h in the box
so 20x20xh = 75000
h =18.75(cm)
The volumn of the stone is
20x20x(20 -18.75) = 500(cm3)

Ans>The volumn of the stone is 500cm3

Should you have any question(s), please feel free to advise me.

JC

2010-01-21 18:56:40 補充：
So sorry typing mistake:

2. The volume of the brick = the volume of the water that has been increased
=30x30x0.01x100=900cm3 (Note, we have to change 0.01m into 1cm)
Let the thickness of the brick be d
then 15x10xd=900
d=6(cm)
Ans> The thickness of the brick is 6cm

1.(10x10x1)/40
=100/40
=2.5(cm3)

2.唔明,什麼是"水位上升了0.01m這塊磚厚"?

3.20x20x20-7.5x1000
=8000-7500
=500(cm3)