Maths 勁人！過黎搵30分啦！ (急!)

2008-06-04 1:51 am

1. A is 20% more than B, what percentage of A is B?
2.If number A increases by 25%, it is equal to number B. Find the percentage of the original value of A to B.
3.The marked price of a dress is $300. By what percentage should the marked price be increased so that the selling price is $300 after giving a discount of 20%?
4. A watch which costs $1000 is sold at a profit of 60%
( a ) Find the selling price of the watch.
( b ) By increasing the marked price, the watch will be sold at a 20% discount in order to keep the profit at 60%. What is the percentage increse of the marked price?

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回答 (1)

None

2008-06-04 2:57 am

✔ 最佳答案

1

A = (1+20%)B
B = A/1.2
B = (5/6)(100%) A
B = 86.67% of A

2

(1+25%)A = B
A= B/1.25
A= (1/1.25)(100%)B
A= 80% of B

3
Let $y be the new marked price

(y)(1-20%)=300
y=300/(80%)
y=375

Therefore the increase value of the new marked price should be 375-300 = $75

4
a)
selling price = $1000(1+60%) = $1600

b
Let $a be the new marked price

a(1-20%) = 1600
a=(1600)/(80%)
a=2000

The increase of new marked price
= [(new marked price - original marked price)/(original marked price)] x 100%
= [(2000-1600)/1600] x100%
= (400/1600) x100%
= 25%

2008-06-03 19:01:13 補充：
沒想到什麼解釋只有這些

cost = 成本
profit = 售價 - 成本
selling price = 實際售價
marked price = 標價如無折扣時實際售價=標價有折扣時售價= 標價減折扣

2008-06-03 21:30:21 補充：
一時不慎計錯數

1應該是

B = (5/6)(100%) A
B = 86.67% of A (誤)
B = 83.33% of A (正)

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