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I am taking a weird math course, "Introduction to Logic for Computer Science". My head hurts! Here is an example found on the first page of the textbook:Mary has twice as many apples as John. Mary throws half of her apples away, because they are rotten, and John eats one of his. Mary still has twice as many apples as John. How many apples did Mary and John have initially?
I can never solve this kind of problems using pen and paper. I think about Mary's and John's apples at the same time, and that is where the troubles really start . . . and why should I care if her apples are rotten or not?
:: Sasha, at 08:43 pm on Sunday, 19. October 2003
Here's the answer: Why did Mary even let the apples get rotten in the first place? She shoulda baked an apple pie and saved herself some trouble. =)
:: rhun, at 11:42 pm on Sunday, 19. October 2003
Mary has 4 and John has 2. Mary throws half (2) of them, and John eats 1 of them, so on the end he has 1 and she has 2, still twice as many apples as John. Right?
:: Igor, at 02:43 am on Monday, 20. October 2003
The most important thing is to set properly equotions.
Let say: Mary has X apples and John has Y.
Mary has twice as many apples as John.
X = 2*Y (This is Eq. 1.)
Mary throws half of her apples away, because they are rotten, and John eats one of his. Mary still has twice as many apples as John.
X/2 = 2*(Y-1) (This is Eq. 2.)
From Eq. 1 instead of X we can write 2*Y in 2'nd Eq.
Y*2/2 = 2*(Y-1)
Y = 2*Y - 2
-Y = -2
Y = 2
Now we go back to Eq. 1
X = 2* Y = 2*2 = 4
X = 4
As you can see there is only one real solution and enybody is willing to find complex solutions?
:: zoka, at 04:49 am on Monday, 20. October 2003
Thank you Zoka :-)
I should take some math tutorials from you, you seem to be good.
:: Sasha, at 08:43 am on Monday, 20. October 2003
You are welcome.
You can add math tutorials section to your "Howto" section.
:: zoka, at 07:13 pm on Monday, 20. October 2003
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