推 weichieh:高竿 06/27 11:08
推 piwei:真是豁然開朗 多謝 06/27 23:46
推 onznka:唔 sorry 題目沒看清楚...@@ 06/28 09:19
→ onznka:感謝糾正! 06/28 09:19
※ 引述《piwei (what happen)》之銘言：
: The cost of a square slab is proportional to its thickness and also
: proportional to the square of its length. What is the cost of a square slab
: that is 3 meters long and 0.1 meter thick?
: 1) the cost of s square slab that is 2 meters long and 0.2 meter thick is$160
: more than the cost of a square slab that is 2 meters long and 0.1 meter thick.
: 2)The cost of a square slab that is 3 meters long and 0.1 meter thick is$200
: more than the cost of a square slab that is 2 meters long and 0.1 meter thick.
: 答案是D
: 我覺的是E(天差地遠的)
: 麻煩幫忙解答一下 頭都快想破掉了
我的想法跟樓上不太一樣
cost 與 thickness 成正比且與 length 平方成正比
所以 1) 假設 2 meter long, 0.2 meter thick 的 slab 為 X
所以 2 meter long, 0.1 meter thick 的 slab 則為 X/2
X-X/2 = 160 可得X為320
2 meter long, 0.1 meter thick 為160 (320/2)
題目問 3 meter long, 0.1 meter thick 則為 160 * (3/2)的平方
所以答案為360
2) 相同假設 3 meter long, 0.1 meter thick 的 slab 為 X
所以 2 meter long, 0.1 meter thick 的 slab 則為 X * 4/9
X - 4/9*X = (5/9)X = 200
可得X = 360
以上是我的想法 有錯請指正 ^^
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