Compounding Interest: Confirm my answers?

[eleventhxhour]

Find the missing information:

1) P = 3800, r = 8%, t = 39 months, c = quarterly, A = ?
2) P = ?, r = 7.5%, t = 2 years, c = monthly, A = 5,000
3) P = ?, r = 5.2%, t = 3 years, c = weekly, A = 3000
4) P = 3723, r = 6.75%, t = 30 months, c = semi annually, A = ?

My answers were:
1) A = 4912
2) P = 4306
3) P = 2566
4) A = 4395

Can someone confirm that my answers are correct? (you don't have to do all of them, but it would be really helpful! Also it said P or PV and A or FV in the question - I just wrote P and A)

 

[MarkFL]

The formula we may begin with is:

$$A=P\left(1+\frac{r}{n}\right)^{nt}$$

the other form we will need is:

$$P=A\left(1+\frac{r}{n}\right)^{-nt}$$

1.) $$A=3800\left(1+\frac{0.08}{4}\right)^{4\cdot3.25}\approx4915.71$$

2.) $$P=5000\left(1+\frac{0.075}{12}\right)^{-12\cdot2}\approx4305.55$$

3.) $$P=3000\left(1+\frac{0.052}{52}\right)^{-52\cdot3}\approx2566.88$$

4.) $$A=3723\left(1+\frac{0.0675}{2}\right)^{2\cdot2.5}\approx4395.12$$