后天杀鸡,急问prep输血二道，多谢

tracystar

后天杀鸡，现在感觉脑子秀豆了。百思未得其解，请教NN，谢谢。

1。问一物品在哪家店更便宜价格多少，一家是$90, a 10% discount, plus 10% tax on discounted price;另一家是$90, a 10% sales tax, 10% rebate after tax.  
答案是$89.00, 俺怎么算来算来都是89.1呢，求算法。

2。 A hiker walking @ a constant rate of 4 miles per hour was passed by a cyclist traveling in the same direction along the same path @ a constant rate of 20 miles per horu. C stops to wait for H 5 minutes after passing her while H continues to walk @ her constant rate. How many minutes must C wait until H catches up?
15  20  25
求思路。

tracystar

多谢爱爱。

1还有疑问，prep上的答案是89.0，不知怎么来的？prep库里也会出错？
90*110%*90%不也是89.1 吗？

爱爱

2.首先.找出两者之间的距离差20-4)*5/60
再次求:时间=距离/速度= 上式/4 =20/60hr =20minutes
1.90*90%*110%=89.1    90*110%*90%=90.1