200分求一道数学题,懂英文的高手来呀A telephone company charges customers a certain amount for the first minute of a long distance call and another amount for each additional minute.A customer makes two calls to the same city—a 30-minu

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200分求一道数学题,懂英文的高手来呀A telephone company charges customers a certain amount for the first minute of a long distance call and another amount for each additional minute.A customer makes two calls to the same city—a 30-minu
200分求一道数学题,懂英文的高手来呀
A telephone company charges customers a certain amount for the first minute of a long distance call and another amount for each additional minute.A customer makes two calls to the same city—a 30-minute call for $2.75 and a 15-minute call for $1.40.
(a) Determine the cost for the first minute and the cost for each additional minute.
cost for the first minute 多少¢
cost for each additional minute 多少¢
(b) If there is a federal tax rate of 3.6% and a state tax rate of 7.8% on all long distance calls,find,to the nearest minute,the longest call to the same city whose cost will not exceed $5.00.
The longest call is 多少minutes long.

200分求一道数学题,懂英文的高手来呀A telephone company charges customers a certain amount for the first minute of a long distance call and another amount for each additional minute.A customer makes two calls to the same city—a 30-minu
(a)列2元一次方程:
x+29y = 2.75
x+14y = 1.4
==>x=0.14,y=0.09
cost for the first minute = 0.14$
cost for each additional minute = 0.09$
(b) (1+11.4%)*[0.14+(x-1)*0.09]

a)30分钟用了2.75，,15分钟用了1.40，所以后来的每分钟是（2.75-1.40）除以15，也就是每分钟0.09美元，那么14分钟用了1.26，故第一分钟用了0.14
b）具体数没算，但是方法是：两个政府总共收了你11.4%的税，你可以先用5除以111.4%，之后得出来的前就相当于不算税的，你按照第一问的情况算就行...

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题目意思：通信公司收费政策是通话第一分钟符一定费用，没多一分钟就增加一定费用。一个人向同一城市打了两个电话，一次是30分钟，花了2.75美元，一次是15分钟,花了1.4美元。
问：（a）第一分钟多少钱，每增加一分钟多少钱？
（b）如果联邦政府收税3.6%，州政府收税7.8%，试求费用不超过5美元的最长通话时间是多少？

（a）一次是30分钟，花了2.75美元，一次是15分钟,花了1.4美元，所以(2.75-1.4)/15就是每增加一分钟所花的钱，为0.09；1.4-0.09*14=0.14就是第一分钟所花的钱。
（b）设最长通话时间T，列方程，(0.14+(T-1)*0.09)*1.114=5,求得T=49分钟，因为题目要求取整。

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是

设 the first minute = x ¢，each additional minute = y ¢
x+29y=2.75
x+14y=1.4
一式 - 二式得 15y=1.35 ，所以 y=0.09 $=9 ¢ ，x=14 ¢
(a) cost for the first minute 14¢

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设 the first minute = x ¢，each additional minute = y ¢
x+29y=2.75
x+14y=1.4
一式 - 二式得 15y=1.35 ，所以 y=0.09 $=9 ¢ ，x=14 ¢
(a) cost for the first minute 14¢
cost for each additional minute 9¢
设最长时间为 t 分钟
[0.14+0.09(t-1)]*(1+3.6%+7.8%)≤5
0.14-0.09+0.09t ≤ 4.48833
0.09t ≤ 4.48833-0.05
t ≤ 4.43833/0.09
t ≤ 49.315
t 最长为 49 分钟

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电话公司的客户一定数量的指控第一分钟的长途电话,另一项金额为每一个额外的每一分钟。一个客户打造两个调用相同的极大的30分钟电话为2.75美元,1.40美元一个15分钟的电话。
　　(a)确定成本和费用第一分钟每增加一分钟。
　　第一分钟多少成本？
(b)如果有一个联邦税率为3.6%,国家7.8%的税率在所有长途电话,查找,到最近的分钟,最长的电话到同一城市的费用不会超过$ ...

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1.cost for the first minute $0.14
2 cost for the additional minute $0.09
(30-15=15minute,2.75-1.40=1.35,1.35/15=0.09,15-1=14,1.40-14*0.09=0.14)
B问题不能理解他的联邦税率和州税率之间的关系。不懂。

假设第一分钟x元，其余时间每分钟y元
则有 x+29y=2.75 x+14y=1.4 解得x=0.14 y=0.09
所以第一分钟0.14元，其余每分钟0.09元
第二题假设客户打电话x分钟，则有[0.14+0.09*（x-1）]*（1+0.036+0.078）=5
可解得x=49.13 所以最多可以打49分钟左右

而特瑞特让他

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