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# Geometric progression Question watch

1. The question states a Road company are making an effort to reduce accidents on the motorway and the stats are as follows

year 2000: 1000 accidents 2001: 900 accidents 2002: 810 accidents

Part 2 of the question is asking how many accidents in the year (2000+n).

I know that Un=1000x0.9^(n-1) from Part 1, so what exactly is being asked of me in Part 2?
2. (Original post by kneestochest)
The question states a Road company are making an effort to reduce accidents on the motorway and the stats are as follows

year 2000: 1000 accidents 2001: 900 accidents 2002: 810 accidents

Part 2 of the question is asking how many accidents in the year (2000+n).

I know that Un=1000x0.9^(n-1) from Part 1, so what exactly is being asked of me in Part 2?
try some values for your n

e.g what year is year 2005?
which term is it?
3. (Original post by TeeEm)
try some values for your n

e.g what year is year 2005?
which term is it?
Part 1 asks you to find the accidents in 2004 which i labelled as U5.

Do you know what the exercise is asking for here? I can only assume it wants the formula I mentioned but seeing as i needed to create it for Part 1, Part 2 seems redundant..?
4. (Original post by kneestochest)
Part 1 asks you to find the accidents in 2004 which i labelled as U5.

Do you know what the exercise is asking for here? I can only assume it wants the formula I mentioned but seeing as i needed to create it for Part 1, Part 2 seems redundant..?
5. (Original post by kneestochest)
Part 1 asks you to find the accidents in 2004 which i labelled as U5.

Do you know what the exercise is asking for here? I can only assume it wants the formula I mentioned but seeing as i needed to create it for Part 1, Part 2 seems redundant..?
No one said you had to construct the formula for part 1. You could have just spotted the pattern and kept multiplying by 0.9 four times.

Some people have trouble expressing the formula mathematically, but could use it iteratively by hand (which is obviously tragic if say you wanted to know what was going on in year 4000) so part 2 is just checking you can actually mathematically formulate it.
6. (Original post by In One Ear)
No one said you had to construct the formula for part 1. You could have just spotted the pattern and kept multiplying by 0.9 four times.

Some people have trouble expressing the formula mathematically, but could use it iteratively by hand (which is obviously tragic if say you wanted to know what was going on in year 4000) so part 2 is just checking you can actually mathematically formulate it.
Thanks for replying. Is my formula incorrect though? The above poster thinks it is but hasn't said why.
7. (Original post by kneestochest)
Thanks for replying. Is my formula incorrect though? The above poster thinks it is but hasn't said why.

EDIT:

Your exponent is wrong, should be be 0.9^n (think about the year 2000, this correlates to n=0 in the whats happening in the year 2000+n format). What is 1000*0.9^(0-1) (as in your formula)?

I suspect you have just made that error because you initially constructed the formula with 2000 being the first term, 2001 being the second etc. But now all your years are one iteration of the formula out because part 2 calibrates it so that 2000 is the n=0 (zeroth) term.

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Updated: February 3, 2016
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