1.the radii of two solid spheres made of the same material are in the ratio2:3. If the smaller sphere weight 16 kg,then find the larger one weighs?????
2.given that X不等於0 and 負x,x,3x^2 are in G.P., find X?什麼是 G.P.?
以上 兩題請列明步驟thx
呢兩條數點計?
2008-08-26 9:51 pm
回答 (1)
2008-08-26 10:21 pm
✔ 最佳答案
1)Volume of a sphere = 4/3 pi r^3
mass =Vp, where p is the density
So if r1:r2=2:3, then V1:V2=r1^3:r2^3=8:27
and m1:m2=V1:V2
if m1=16, then m2=16/8 x 27=54kg
2) example of GP:
a, 2a,4a, 8a,16a,.....
b,3b,9b,27b,.....
The two number are different by the same factor
For x <> 0,
-x,x,3x^2 are in GP
x/-x=-1
3x^2/x=x/-x=-1
3x=-1
x=-1/3
checking
-x=1/3
x=-1/3
3x^2=3(1/9)=1/3
They are GP in a factor of -1.
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