plz help~

2007-12-06 2:54 am
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~

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 5:10 am
725x3-810x2
=2175-1620
=555

The third pair cost$555
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 !


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