I'm using the Charles P. McKeague "Algebra with trigonometry for College Students" (Second Edition)
you made two errors,
1. you multiplied by 100 4 times.
2. you didn't use the binomial theorem to expand the binomial
Using the expansion you should get.
$\displaystyle (1+r)^4 = 1 + 4r + 6r^2 + 4r^3 + r^4$
may be worth reading over your books notes on the binomial expansion.
Let us know if you have any further problems.
bobak