Secondary 4 eMaths question

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Secondary 4 eMaths question

Postby bluesky63 » Sat Oct 01, 2011 3:19 pm

hi,
Can someone help to solve this question

Mr Lai take X mins to carve a block of ice to swan, Mr Han takes 25 mins more to carve the same size of ice block to swan. if they carve the block of ice together only take 30 Mins to complete. derive all the above to the following equation
X^2-35X-750 = 0

bluesky63
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Re: Secondary 4 eMaths question

Postby FrekiWang » Sat Oct 01, 2011 11:29 pm

In 1 mins, Mr Lai can carve 1/X block and Mr Han can carve 1/(X+25) block
When they are working together,
In 1mins they can carve a total of 1/X+1/(X+25) block, and when this value is mutiplied by 30(mins), it will be equal to 1 block.

30[1/X+1/(X+25)]=1, mutiply both sides by X(X+25), re-arrange, we show the result.

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Re: Secondary 4 eMaths question

Postby bluesky63 » Sun Oct 02, 2011 11:48 am

Oh yes, thank you very much.

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