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# C4 exponential change question help watch

1. I'm stuck on the following question, 4c(i)

I do not understand how to form the 2 equations to equal eachother to show what T equals.
Here is the markscheme for reference:

I understand why it makes them both equal together but I do not understand why it is T-10 on the p, I tried with T + 10 on the q but it didn't work, why is it this way? Thanks
2. (Original post by Sayless)
I understand why it makes them both equal together but I do not understand why it is T-10 on the p, I tried with T + 10 on the q but it didn't work, why is it this way? Thanks
The reason it doesn't work the other way round is because is the April 1st 2001, as specified in the question.
3. (Original post by joostan)
The reason it doesn't work the other way round is because is the April 1st 2001, as specified in the question.
In the second equation when t = 0, it is April 1st 1991, how do I know which one to put it in
4. (Original post by Sayless)
In the second equation when t = 0, it is April 1st 1991, how do I know which one to put it in
Sorry, I didn't make myself very clear, the formula for uses in 2001, so you need to adjust the time value of the formula for by , so if the time is years after 1991, then it is years after 2001.

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