Running at their respective constant rates, machine X takes 2 days longer to produce w widgets than machine Y. At these rates, if the two machines together produce 5/4 w widgets in 3 days, how many days would it take machine X alone to produce 2w widgets?
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方程法:列出1/y代表y的速度。1/y+2等于x的速度。
列出3*(1/y+1/y+2)=5/4 求出y
代入法:
把每个数带入。等于5/4的就是答案。
例如:当6天x机器可以produce2w,那x机器1w需要3天,y则需要3-2=1.
带去就是3*(1/3+1)不等于5/4
所以不成立 再试下一个。
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