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pls help p.6 maths [複製鏈接]

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mocha815


男爵府

積分: 6832


1#
發表於 08-1-10 17:42 |只看該作者
9 rulers and 6 erasers cost $58.5 altogether.
6 rulers and 3 erasers cost $36.0 altogether.
find the sum of the cost of a ruler and an eraser.
i know the rulers is $4.5 and an eraser is $ 3,
but i don't know how to list
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mum-LCC


侯爵府

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8#
發表於 08-1-10 22:02 |只看該作者
原文章由 swkmc 於 08-1-10 18:28 發表
oh, i thought is to find out the cost of ruler + erasers separately tim~
i originally use this but i thought, how can find out the cost of two separately~

thanks~~


swkmc: you overlooked the Question which asks to find only the sum of the cost of a ruler and an eraser. But you are very smart to find out each of their cost.
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swkmc


大宅

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7#
發表於 08-1-10 18:28 |只看該作者
oh, i thought is to find out the cost of ruler + erasers separately tim~
i originally use this but i thought, how can find out the cost of two separately~

thanks~~
原文章由 kuno 於 08-1-10 18:02 發表


then

rulers + erasers = 22.5/3 = 7.5
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kuno


複式洋房

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6#
發表於 08-1-10 18:02 |只看該作者
原文章由 8C9 於 08-1-10 17:55 發表
9 rulers + 6 eraser = $58.5
- 6 rulers + 3 erasers = $36
-------------------------------------
3 rulers + 3 erasers = $58.5 - $36 = $22.5


then

rulers + erasers = 22.5/3 = 7.5

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mocha815


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5#
發表於 08-1-10 17:56 |只看該作者
thanks :-P :-P
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8C9


大宅

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4#
發表於 08-1-10 17:55 |只看該作者
9 rulers + 6 eraser = $58.5
- 6 rulers + 3 erasers = $36
-------------------------------------
3 rulers + 3 erasers = $58.5 - $36 = $22.5
=> ruler + erasers = $22.5/3 = $7.5

原文章由 mocha815 於 08-1-10 17:42 發表
9 rulers and 6 erasers cost $58.5 altogether.
6 rulers and 3 erasers cost $36.0 altogether.
find the sum of the cost of a ruler and an eraser.
i know the rulers is $4.5 and an eraser is $ 3,
but i do ...

[ 本文章最後由 8C9 於 08-1-10 18:04 編輯 ]
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swkmc


大宅

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3#
發表於 08-1-10 17:51 |只看該作者
唔知係未, 因我好耐無計數
X= Ruler
Y= Eraser
9X+6Y=58.5
&
6X+3y=36
3(2X+y)=36
2X+Y=12
Y=(12-2X)
substitute to 1st equation
9X+6Y=58.5
9X+6(12-2X)=58.5
9X+72-12X=58.5
3X=13.5
X=4.5
Since Y=(12-2X)
Y=12- 2(4.5)
Y=3
mud p6 o甘complicated???
有無d快d既方法?
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mocha815


男爵府

積分: 6832


2#
發表於 08-1-10 17:48 |只看該作者
原文章由 mocha815 於 08-1-10 17:42 發表
9 rulers and 6 erasers cost $58.5 altogether.
6 rulers and 3 erasers cost $36.0 altogether.
find the sum of the cost of a ruler and an eraser.
i know the rulers is $4.5 and an eraser is $ 3,
but i do ...

help! help!
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