# Math Help - log application problem

1. ## log application problem

a couple wants to have $40,000 in 5 years for a down payment on a new house. a) how much could they deposit today, at 6.4% compounded quarterly, to have the required amount in 5 years? b)how much interest will be earned? c)if they can deposit only$20,000 now, how much more will they need to complete the $40,000 after 5 years? 2. Originally Posted by shannon1111 a couple wants to have$40,000 in 5 years for a down payment on a new house.

a) how much could they deposit today, at 6.4% compounded quarterly, to have the required amount in 5 years?

b)how much interest will be earned?

c)if they can deposit only $20,000 now, how much more will they need to complete the$40,000 after 5 years?
part (a) ...

$A = A_0\left(1 + \frac{r}{n}\right)^{nt}$

$40000 = A_0\left(1 + \frac{.064}{4}\right)^{20}$

$A_0 = \frac{40000}{\left(1 + \frac{.064}{4}\right)^{20}}$

$A_0 \approx 29120 \, dollars$

you do the rest.

3. Originally Posted by skeeter
part (a) ...

$A = A_0\left(1 + \frac{r}{n}\right)^{nt}$

$40000 = A_0\left(1 + \frac{.064}{4}\right)^{20}$

$A_0 = \frac{40000}{\left(1 + \frac{.064}{4}\right)^{20}}$

$A_0 \approx 29120 \, dollars$

you do the rest.
I figure out the question b ,but I can go on to question c.....

can someone help me about the part c?plz!!~ thanks

4. Originally Posted by shannon1111
I figure out the question b ,but I can go on to question c.....

can someone help me about the part c?plz!!~ thanks
(c) ...

$40000 - 20000\left(1+\frac{.064}{4}\right)^{20}$

5. thanks!~