Math Questions

2010-11-03 8:09 am

please to solve the following questions:

1.A blanket loses 8% of its length and 10% of its widt after washing.
Find the percentage loss in its area.

2. Let s=vt. If v is increased by 8% and t is decreased by 12%, then the percentage
change in s, correct to the nearest integer, is

3.A number, when increased to y, is increased by x%. Find this number in terms
of x and y.

4. Suppose that x is first increased by 50% and then decrease by 50% to x,
whereas y is first decreased by 50% and then increased by 50% to Y.
If x = y, find the ratio X:Y

5. The area of a square picture is 121% of the original after enlargement.
What is the percentage increase in the length of its sides after enlargement?

6. A hawker sells a kind of clothing at a marked price 30% higher than the cost
price, and then offers a 15% discount to the customers. If the makes a profit of
$12.6 for each piece of clothing sold on discount, what is the cost of each
piece of clothing?
7. Last year, the price of a stock certificate was decreased by 30%. This year, its
price is further decreased by 20%. The percentage change in the price of this
stock certificate is?

回答 (1)

用戶26240

2010-11-03 9:31 am

✔ 最佳答案

1.
Let L and W be the length and the width respectively.

Original area = LW
New area = (1 - 8%)L x (1 - 10%)W = (82.8%)LW
% loss in area = (100 - 82.8)% = 17.2%

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2.
Original s = vt
New s = (1 + 8%)v x (1 - 12%)t = (95.04%)
% change in s = (95.04 - 100)% = -5% (to the nearest integer)

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3.
Let n be the number.

n(1 + x%) = y
n = y/(1 + x%)
The number = y/(1 + x%)

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4.
x(1 + 50%)(1 - 50%) = X ….. (1)
y(1 - 50%)(1 + 50%) = Y ….. (2)

(1)/(2):
x/y = X/Y

If x = y, then X : Y = 1 : 1

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5.
Let A be the original area.

Original length of side = √A
New length of side = √(121%)A = √1.21A = 1.1√A = 110%√A
% increase in length = (110 - 100)% = 10%

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6.
Let $c be the cost of each piece of clothing.

c(1 + 30%)(1 - 15%) - c = 12.6
0.105c = 12.6
c = 120

Cost of each piece of clothing = $120

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7.
Let $p be the price of the stock certificate.

New price of the stock certificate
= $p(1 - 30%)(1 - 20%)
= $0.56p
= (56%)$p

The % change in the price of this stock certificate
= (56 - 100)%
= -44%

參考: 土扁

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