#### Answer

$r=0.75\%$

#### Work Step by Step

We know that the simple interest formula is:
$Interest=Principal*Rate*Time$
$I=prt$
We solve for the rate, $r$:
$\displaystyle r=\frac{I}{pt}$
And plug in $I=25.5$, $p=3400$, and $t=1$:
$r=\frac{25.5}{3400*1}$
$=0.0075$
$=0.75\%$