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| 2017/05/25 21:02:22瀏覽62｜回應0｜推薦0 | |
| 標題: 數學－百分比的算法
此文章來自奇摩知識+如有不便請留言告知 發問:Q1: what is the percent increase in the average ( arithmetic mean) contribution per member of a certain public radio station from 1985 to 1995 ?條件1:Total contributions by members increased from $505,210 in 1985 to $1,225,890 in 1955.條件２:The number of members exactly doubled from 1985 to... 顯示更多 Q1: what is the percent increase in the average ( arithmetic mean) contribution per member of a certain public radio station from 1985 to 1995 ? 條件1:Total contributions by members increased from $505,210 in 1985 to $1,225,890 in 1955. 條件２:The number of members exactly doubled from 1985 to 1995. 答案是：兩個條件樣相加起來才能成立。 我不能理解為什麼能增加百分比耶 請告訴我謝謝。 最佳解答: 另一個有趣的解法如下: 1,225,890/505,210=2.42650 (95'捐款為85'的2.42650倍) 2.42650/2=1.21325 (95'平均每人捐款為85'的1.213倍) 所以成長了(1.213-1)*100%=21.3% 2008-12-25 09:34:12 補充： Lai已經回答得很正確, 在此再補充下列算法: 設85'捐款人數有N人, 每人平均捐款為 (505,210/N) 95'捐款人數有2N人, 每人平均捐款為 (1,225,890 /2N) >> 每人平均捐款百分比為: {[(1,225,890 /2N) - (505,210/N)] / (505,210/N)} * 100% = (612945-505210) / (505,210) * 100% (>>若改成通分母"2N", 再消去"2N", 即為Lai的解法: (1,225,890-1,010,420)/1,010,420*100% = 21.3% 其他解答: 條件1的年份是否應是1985~1995. 如果不是就很怪了. 如果是的話,我的想法如下: 1985年的總捐款是505,210. 1995年會員增加兩倍，假設每個會員捐款不變， 則總捐款應是 505,210*2=1,010,420. 但1995年的總捐款實際上是 1,225,890. 所以捐款增加了 1,225,890-1,010,420=215,470. 每個人增加的捐款百分比是 215,470/1,010,420=0.2132479 平均約增加了21.3% |
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