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枫下家园 / 望子成龙 / 孩子的作业,帮忙看看这道题吗?多谢!Devin and Nicholsa can finish a piece of work in 15days.Devin can do the job himself in 18days.If Nicholas wanted to do the job alone,how long would it take him?
-free1(转战南北);
2006-12-8
{161}
(#3366989@0)
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一天一个苹果,devin 18 天吃完,所以有18个苹果。加上nico 15天吃完,,所以 nico 15 天吃3个苹果,nico 每天吃 3 /15=0.2 个苹果。 如果只有nico吃,就要 18 / 0.2 天吃完。
-c1xwy(洪兴罩俺去战斗);
2006-12-8
(#3367002@0)
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1/x+1/Y=1/15
1/x=1/18
这个对吗?
-free1(转战南北);
2006-12-8
(#3367004@0)
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x,y 每天工作量,15x + 15y = 1 , 18x = 1 , ?1/y
-c1xwy(洪兴罩俺去战斗);
2006-12-8
(#3367013@0)
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明白了,谢谢!
-free1(转战南北);
2006-12-8
(#3367027@0)