200分求一道数学题,懂英文的高手来呀
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 $5.00.
The longest call is 多少minutes long.
问答/185℃/2024-05-13 18:25:01
优质解答：
(a)列2元一次方程:
x+29y = 2.75
x+14y = 1.4
==>x=0.14,y=0.09
cost for the first minute = 0.14$
cost for each additional minute = 0.09$
(b) (1+11.4%)*[0.14+(x-1)*0.09]