SOLUTION: Cybthia's donates oranges to a senior home. In week 1 she took 1/10 of the total of her oranges to the senior home; she took 1/9 of the left over oranges in week 2; she took 1/8 of

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Question 1077548: Cybthia's donates oranges to a senior home. In week 1 she took 1/10 of the total of her oranges to the senior home; she took 1/9 of the left over oranges in week 2; she took 1/8 of the left over oranges in week 3; she took 1/7 of the left over oranges in week 4 and so on until week 9. In week 9 she took 1/2 of the left over oranges; and she took all 10 left over oranges from the tree in week 10. What was the total number of oranges on the tree at the beginning?
I worked on it and got 100 but I need a formula. I am not sure how to make it a formula. Or a model.

Found 2 solutions by jorel1380, MathTherapy:
Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
Let x be the amount of oranges originally on the tree. Then, the equation you are looking for would be:
x(9/10)(8/9)(7/8)(6/7)(5/6)(4/5)(3/4)(2/3)(1/2)-10=0
So:
x(9/10)(8/9)(7/8)(6/7)(5/6)(4/5)(3/4)(2/3)(1/2)=10
.1x=10
x=100
There were 100 oranges originally. ☺☺☺☺

Answer by MathTherapy(10549) About Me  (Show Source):
You can put this solution on YOUR website!
Cybthia's donates oranges to a senior home. In week 1 she took 1/10 of the total of her oranges to the senior home; she took 1/9 of the left over oranges in week 2; she took 1/8 of the left over oranges in week 3; she took 1/7 of the left over oranges in week 4 and so on until week 9. In week 9 she took 1/2 of the left over oranges; and she took all 10 left over oranges from the tree in week 10. What was the total number of oranges on the tree at the beginning?
I worked on it and got 100 but I need a formula. I am not sure how to make it a formula. Or a model.
1st week: Remainder = 1+-+1%2F10+=+9%2F10
2nd week: Remainder = %288%2F9%29+%2A+%289%2F10%29+=+8%2F10
3rd week: Remainder = %287%2F8%29+%2A+%288%2F10%29+=+7%2F10
Do you now see a pattern/sequence? If not, I do!
Term/Week 1: Remainder = %2810+-+1%29%2F10+=+9%2F10
Term/Week 2: Remainder = %2810+-+2%29%2F10+=+8%2F10
We can then say that the REMAINDER-rule is: matrix%281%2C3%2C+a%5Bn%5D%2C+%22=%22%2C+%2810+-+n%29%2F10%29, with n being the term/week number
Term/Week 9, or matrix%281%2C3%2C+a%5B9%5D%2C+%22=%22%2C+%2810+-+9%29%2F10+=+1%2F10%29
Week 9’s remainder is also the amount she had at the beginning of week 10
Therefore, with original number of oranges being Y, we can say that: