1. Two shops sell the same brand of chocolate at the same price.Today they both cut down its price.Shop A lowers the price by 30%,and increases by 30%after a week.Likewise,shop B lowers the price by 40%,and increases by 40% after a week.Are the prices of the chocolate at the two shops still the same after a week?
我要式同過程..thx alot
maths f.1 percentages
2007-09-13 10:31 pm
回答 (2)
2007-09-13 11:02 pm
✔ 最佳答案
1. if the price of chocolate is Xshop a: Today :x*(1-30%)=$ 0.7x
after a week: $ 0.7x *(1+30%)=0.91x
shop b: Today :x*(1-40%)=$ 0.6x
after a week: $ 0.6x *(1+40%)=0.84x
SO the prices of the chocolate at the two shops ARE NOT still the same after a week
2. 30*(1-r%)=20
r=1-(20/30) *100%
=33%
2007-09-13 10:51 pm
let the price is x,
the price of A= [x(70%)](130%)=[x(70/100)](130/100)=91x/100
the price of B= [x(60%)](140%)=[x(60/100)](140/100)=84x/100
therefore, the price of the chocolate at the two shops are not the same after a week. B is now cheaper than A.
2007-09-13 14:58:13 補充：
30(1-r) = 2030-30r = 2030= 30r + 20(10/30) = 30r(1/3) = rr = 0.33(2 d.p.) Therefore, r equal to 33 percent.
the price of A= [x(70%)](130%)=[x(70/100)](130/100)=91x/100
the price of B= [x(60%)](140%)=[x(60/100)](140/100)=84x/100
therefore, the price of the chocolate at the two shops are not the same after a week. B is now cheaper than A.
2007-09-13 14:58:13 補充：
30(1-r) = 2030-30r = 2030= 30r + 20(10/30) = 30r(1/3) = rr = 0.33(2 d.p.) Therefore, r equal to 33 percent.
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