Miss Wong has 3 pairs of glasses.Each pair costs $725 on average.If the average price of the first and the second pairs is$810,how much does the third pair cost?
Use average~
plz help~
2007-12-06 2:54 am
回答 (3)
2007-12-06 3:02 am
✔ 最佳答案
725x3-810x2=2175-810x2
=2175-1620
=555
Answer:The third pair of glasses cost $555.
hope I can help you!
參考: Me
2007-12-06 3:10 am
let :
(A + B + C)/3 = 725 ---(1), and
(A + B)/2 = 810 ---(2)
then use (2),
(A + B)/2 = 810 ---> A + B = 1620 ---(3)
so, A = 1620 - B --- (4)
use (4) and sub. it into (1),
((1620 - B) + B + C)/3 = 725 --->
(1620 - B + B + C) = 2175 ---> so,
1620 + C = 2175 --->
therefore, C = 2175 - 1620 --->
C = $550
2007-12-16 20:16:50 補充：
sorry... sorry... the answer is $555. My mistake, please forgive !
(A + B + C)/3 = 725 ---(1), and
(A + B)/2 = 810 ---(2)
then use (2),
(A + B)/2 = 810 ---> A + B = 1620 ---(3)
so, A = 1620 - B --- (4)
use (4) and sub. it into (1),
((1620 - B) + B + C)/3 = 725 --->
(1620 - B + B + C) = 2175 ---> so,
1620 + C = 2175 --->
therefore, C = 2175 - 1620 --->
C = $550
2007-12-16 20:16:50 補充：
sorry... sorry... the answer is $555. My mistake, please forgive !
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