幾 題 數 學. ,, 好 easy 架!!

１ ::A man sells a carpet for $70 and gains 10%. How much does it cost him?

Original cost
= $70/(1+10%)
= $70/110%
= $70/1.1
= $63.6364 (to 4 dec. place)

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２ ::Mr. Lee sells a car for $50,000 and gains 20%. How much does it cost him?

Original cost
= $50000/(1+20%)
= $50000/120%
= $50000/1.2
= $41666.6667 (to 4 dec. place)

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３ ::What is the selling price of an article costing $10 and being sold at a gain 10.5%?

Selling price
= $10 * (1+10.5%)
= $10 * 110.5%
= $10 * 1.105
= $11.05

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４ ::A merchant bought a dozen pens at $12. At what price must he sell them to make a gain of 20%?

Cost of a pen
= $12/12
= $1

Selling price of a pen
= $1 * (1+20%)
= $1 * 120%
= $1 * 1.2
= $1.2

Selling price of a dozen of pens
= $1.2 * 12
= $14.4


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５ ::A toy which cost $56 was sold at a gain of 12 %. Find the selling price.

Selling price
= $56 * (1+12%)
= $56 * 112%
= $56 * 1.12
= $62.72

2006-12-09 11:20:09 補充：
小小補充：第四題因為沒有說明是一支還是一打的 selling price，所以最好的答案是將兩者都寫出來。

1.::A man sells a carpet for $70 and gains 10%. How much does it cost him?

70×10﹪
=70×0.1
=7

2. ::Mr. Lee sells a car for $50,000 and gains 20%. How much does it cost him?

50000×20﹪
=50000×0.2
=10000

3. ::What is the selling price of an article costing $10 and being sold at a gain 10.5%?

10×(1＋10.5﹪)
=10×0.115
=1.15

１ ::A man sells a carpet for $70 and gains 10%. How much does it cost him?
70/(1+10%)
=70/(110%)
=70/1.1
=700/11
=$63&7/11(mixed number)
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２ ::Mr. Lee sells a car for $50,000 and gains 20%. How much does it cost him?
50000/(1+20%)
=500000/(120%)
=50000/1.2
=500000/12
=125000/3
=$41666&2/3(mixed number)
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３ ::What is the selling price of an article costing $10 and being sold at a gain 10.5%?
10*(1+10.5%)
=10*(110.5%)
=10*1.105
=$11.05
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４ ::A merchant bought a dozen pens at $12. At what price must he sell them to make a gain of 20%?
12*(1+20%)
=12*(120%)
=12*1.2
=$14.4
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５ ::A toy which cost $56 was sold at a gain of 12 %. Find the selling price.
56*(1+12%)
=56*(112%)
=56*1.12
=$62.72
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