Quiz Question of F3 15PT.

2010-03-04 2:02 am

Suppose one side of rectangle ABCD is called x.And another side is called y.
Length of x is increased by 10% and that of y is decreased by 10%.What is the percentage change of the perimeter of rectangle ABCD.

(Please give full step answer)

更新1:

I am not asking for area, so xy plz perimeter of rectangle should be 2(x+y) USE x and y to present the perimeter or x:y is also okay

更新2:

so xy plz ->so no xy plz

回答 (4)

tsoi yan

2010-03-04 2:35 am

✔ 最佳答案

{[X*(1+10%)]*[y*(1-10%)]-xy}/xy*100%
=(x*110%*y90%-xy)/xy*100%
=(xy*0.99-xy)/xy*100%
=xy(0.99-1)/xy*100%
=(0.99-1)*100%
=-1%

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terry

2010-03-13 2:11 am

{[X*(1+10%)]*[y*(1-10%)]-xy}/xy*100%
=(x*110%*y90%-xy)/xy*100%
=(xy*0.99-xy)/xy*100%
=xy(0.99-1)/xy*100%
=(0.99-1)*100%
=-1%

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[匿名]

2010-03-04 3:43 am

old perimetre = xy

new perimeter = x(1 + 10%) y(1 - 10%)
= 1.1x * 0.9y
= 0.99xy

percentage change of the perimeter = (0.99xy - xy) x 100% = - 1%

一條式過:

[x(1 + 10%)y(1 - 10%) - xy] x 100%

= - 1%

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用戶2053

2010-03-04 3:34 am

I think xy should be x+y ?

But we cann't find it as we don't know x : y

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