✔ 最佳答案
V = k r² h , (k為常數) 當
r=4 和 h=30 時,V=160 :
160 = k (4²) (30)
k = 1/3a) 所以 V = (1/3) r² h當V=540和h=45時 ,
540 = (1/3) r² (45)
36 = r²
r = 6
b) 設 r 的 % 變化為 p% , 則V(1 + 36%) = (1/3) [r(1 + p%)]² h
(1/3) r² h (1 + 36%) = (1/3) [r(1 + p%)]² h(1 + 36%) = (1 + p%)²1.36 = (1 + p%)²1.16619 = 1 + p%0.16619 = p%16.619% = p%r 的百分變化為 + 16.6% (答案準確至一位小數)
c)r / 舊 h = 5 / 4 ....(1)
r / 新 h = 4 / 5 ....(2)(1) / (2) :新 h / 舊 h = 25/16
新 h = (25/16) 舊 h;舊 V = (1/3) r² 舊h新 V = (1/3) r² 新 h = (1/3) r² (25/16) 舊 h
V的百分變化= [(新 V - 舊 V) / 舊 V] x 100%= { [(1/3) r² (25/16) 舊 h - (1/3) r² 舊h] / (1/3) r² 舊h } x 100%= [(25/16) - 1] x 100%= 9/16 x 100%= + 56.25%