mensuration

1)
old depth of water is 6 cm. new depth of water is 8 cm.
old volume of water is 1000cm^3.
suppose new volume of water is x.
6^3 / 8^3 = 1000 / x {因為 ratio of volume is x^3 : y^3}
x = 2370.37037 cm^3 簡單少少姐 2370 cm^3
water should be added : 2370 -1000 =1370cm^3

2)
old volume of water is 64cm^3, wet surface area is 40cm^2.
new volume of water is (152+64) 216cm^3, new wet surface area is x

( 64開方3次)^2 / (216開方3次)^2 = 40/ x
[因為 surface area x : surface area y = x^2: y^2.
volume x : volume y = x^3 : y^3 , volume 開方3次再^2= surface area]
x = 90 cm^2
increase in surface area: : 90 - 40 = 50cm^2

3) ans should be 1: 7: 19. yr ans maybe wrong.
slant height of A : slant height of (A+B) : slant height of (A+B+C)
1 : 2 : 3
volume of A : volume of (A+B) : volume of of (A+B+C)
1^3: 2^3 : 3^3
1 : 8 : 27
ratio of the volumes of portions A,B,and C : 1 : (8-1) : (27-8)
=1:7:19

1) The ratio of the height of the water & the height of the water after the water added
= 6 : 8
The ratio of their volume
= 6^3 : 8^3
= 216 : 512
= 27 : 64
Let V be the volume of the water after added
27/64 = 1000/V
V = 2370 cm^3
The volume of water should be added
=2370-1000
=1370cm^3