Using compound interest, it is found that Peter needs to invest $404,054.
The amount of money earned, in compound interest, after t years, is given by:
[tex]A(t) = P\left(1 + \frac{r}{n}\right)^{nt}[/tex]
In which:
In this problem:
The investment made is P, hence:
[tex]A(t) = P\left(1 + \frac{r}{n}\right)^{nt}[/tex]
[tex]840000 = P\left(1 + \frac{0.05}{1}\right)^{15}[/tex]
[tex]P = \frac{840000}{(1.05)^{15}}[/tex]
[tex]P = 404054[/tex]
Peter needs to invest $404,054.
More can be learned about compound interest at https://brainly.com/question/25781328