Re: [問題] 數學 求救
※ 引述《bluesoul92 (Vicky)》之銘言：
: 1. A decorator bought a bolt of defective cloth that he judged to be 3/4
: usable, in which case the cost would be $0.8 per usable yard. If it was later
: found that only 2/3 of the bolt could be used, what was the actualcost per
: usable yard? 答案$0.9
: 2.Three automobiles travel distances that are in the ratios of 1:2:3. If the ratios of the traveling times over these distances for these automobiles are 3:2:1 in the same respective order, what are the ratios og their respective average speeds? 答案 1:3:9
1.
假設a bolt of defective cloth 共 Y yards ,共$X
原本認為有3/4Y可以用
所以每單位yard成本為X / 3/4Y = 0.8
=>X = 0.6Y
現在認為2/3可以用
所以每單位YARD成本為X / 2/3Y , 把X代入
=> 0.6Y / 2/3Y =0.9
2.
速度=距離 / 時間
距離 1:2:3
時間 3:2:1
=>速度 1/3:2/2:3/1 = 1:3:9
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