what's going on here?

allegansveritatem

Full Member
Joined
Jan 10, 2018
Messages
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Here is the problem:
problem.jpg

Here is my solution and my solution checking:
solution1.jpg

I tried this problem various times and always got the same answer. But...shouldn't multiplying the result of the division by 2 come out to 300$? I mean, 264$ isn't even respectably close.
 
Here is the problem:
View attachment 10629

Here is my solution and my solution checking:
View attachment 10630

I tried this problem various times and always got the same answer. But...shouldn't multiplying the result of the division by 2 come out to 300$? I mean, 264$ isn't even respectably close.
Try not using simple interest. If you invest some money (at a constant rate) why would you think that you get the same return on your investment each year? Think compound interest.

BTW, it was very good that you tried to check your work. Always do that!
 
Here is the problem:
View attachment 10629

Here is my solution and my solution checking:
View attachment 10630

I tried this problem various times and always got the same answer. But...shouldn't multiplying the result of the division by 2 come out to 300$? I mean, 264$ isn't even respectably close.

I have to say that my first thought on reading the problem was to check the formula itself! If you solve it for A, you'll find that you get the formula for (compound) interest over two years, just as they say. And then you can use that formula to check your answer.

On the other hand, since they didn't explain much, it's possible that the intent was just to give you a formula to work with. Is the context anything more than an introduction to square roots?
 
Try not using simple interest. If you invest some money (at a constant rate) why would you think that you get the same return on your investment each year? Think compound interest.

BTW, it was very good that you tried to check your work. Always do that!

Well, the formula they seem to want us to use is the one given in the problem. Also, there was no mention of the compound interest formula. so I assumed that the interest was compounded yearly. Maybe I should add the first year's interest to the principle and go through the process again? My brains are too fried by this time of night to do anything but I will try again tomorrow.
 
I have to say that my first thought on reading the problem was to check the formula itself! If you solve it for A, you'll find that you get the formula for (compound) interest over two years, just as they say. And then you can use that formula to check your answer.

On the other hand, since they didn't explain much, it's possible that the intent was just to give you a formula to work with. Is the context anything more than an introduction to square roots?

I do not recognize this as the compound interest formula. But of course it is being compounded yearly...so I think I should have added the first year's interest to the principle and then gone through the process again? I will try again tomorrow when my brains have recovered from a long day's journey (into night?).
This problem comes at the end of a section that introduces radicals.
 
I do not recognize this as the compound interest formula. But of course it is being compounded yearly...so I think I should have added the first year's interest to the principle and then gone through the process again? I will try again tomorrow when my brains have recovered from a long day's journey (into night?).

This problem comes at the end of a section that introduces radicals.

That's what I figured.

Once your mind is recovered, things should become clearer. They don't intend you to do any more than evaluate, so they didn't give every detail about the meaning of the formula; but when you solve for A (assuming you are able to do that -- they probably haven't taught that skill yet), you will probably recognize it. As I said, the formula was entirely unfamiliar to me in the given form, so I didn't trust it until I checked it out; but it looks very familiar when solved.
 
That's what I figured.

Once your mind is recovered, things should become clearer. They don't intend you to do any more than evaluate, so they didn't give every detail about the meaning of the formula; but when you solve for A (assuming you are able to do that -- they probably haven't taught that skill yet), you will probably recognize it. As I said, the formula was entirely unfamiliar to me in the given form, so I didn't trust it until I checked it out; but it looks very familiar when solved.

Here is how I proceeded today, keeping in mind what I learned here yesterday:
solution.jpg
 
Here is how I proceeded today, keeping in mind what I learned here yesterday:
View attachment 10631

Are you aware of the shortcut for compound interest? Rather than calculate the interest as i = Prt and then adding that to P, you can combine that as A = P + Prt = P(1 + rt), so that each period (year in this case) you just multiply by the same thing (1+r since t is 1). So the final amount, in your case, is A = P(1+r)^2.

Have you tried solving for A yet?
 
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