1.Joan had bought a number of pens from a shop for $300 last week. The shop reduced the price of each pen by $0.3 this week. If Joan bought the pens this week, she would buy 20 more pens by paying extra $8. How much was a pen after the price reduction?
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2006-10-28 7:03 pm
回答 (2)
2006-10-28 7:36 pm
✔ 最佳答案
Let x be the price and q be the quantity purched in 300X ． Q = 300 --------- (1)
(X - 0.3) (Q + 20) = 308----------(2)
(2) ====> XQ - 0.3Q + 20X - 6 = 308 --------- (3)
Put (1) into (3) ====> 300 - 0.3Q + 20 X-6 = 308
Q = (20X - 14) / 0.3-------- (4)
Put (4) into (1)
(X) (20X - 14) / 0.3 = 300
20X^2 -14X = 90
20X^2 - 14 X -90=0
10X^2 - 7X - 45 = 0
(2x – 5)(5x + 18) = 0
X = 2.5 or – 3.6 (rejected)
the reduced price is x – 0.3 = 2.2
2006-10-28 11:38:33 補充：
the last steps should be 10X^2 - 7X - 45 = 0 (2x – 5)(5x + 9) = 0 X = 2.5 or – 1.8 (rejected) the reduced price is x – 0.3 = 2.2
2006-10-28 7:26 pm
let x be the no. of pens she bought last week.
let y be the price of each pen after price reduction.
x(y+0.3)=300
(x+20)y-300=8
by solving the two equations,you can find the answer.
let y be the price of each pen after price reduction.
x(y+0.3)=300
(x+20)y-300=8
by solving the two equations,you can find the answer.
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