F.2- F.3 Maths Question.... ( Percentages )

2008-08-19 10:57 pm

All questions need steps .... THX...

1. A computer game software marked at $280 is sold at 20% off. If the
discount is 35% of its cost price , find the profit percent .

2. Flora borrows $36000 from a finance company at 3.75% p.a. simple
interest. If she has to return a total amount of $ 45450 , how long does she
borrow???

3. A cat and a dog are not satisfied with their weights. If the weight of the cat
is increased by 20% while that of the dog is decreased by 10%, their weights will be the same. What % of the dog's original weight is cat's original weight?

回答 (1)

Aman

2008-08-19 11:23 pm

✔ 最佳答案

1.
Let y be the cost

y * 35% = 280 * 20%

y = 280 * 0.2 / 0.35

y = 160

The profit percent

= [280 * (1-20%) - 160] / 160

= 40%

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2.
Let y be the number of year she borrow the money

36000 * 3.75% * y = 45450 - 36000

y = 9450 / 3.75% / 36000

y = 7

She borrows the money for 7 years

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3.
Let D be the dog's original and C be the cat's original weight

D * 0.9 = C * 1.2

so, D = C * 1.2 / 0.9

The % we need

= (C / D) * 100%

= [C / (C * 1.2 / 0.9)] * 100%

= 75%

參考: 我自己計

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