Answer
$ 65\%$
Work Step by Step
Given:
$PV=1000$,
$INT=FV-PV=50$,
the time must be in years : $t=\displaystyle \frac{4}{52}=\frac{1}{13}$ years,
we need to find r.
Use the simple interest formula, solve for r:
$FV=PV(1+rt)$
$FV=PV+PVrt\qquad /-PV$
$FV-PV=PVrt\qquad/\div(PV\cdot t)$
$r=\displaystyle \frac{FV-PV}{PV\cdot t}=\frac{50}{1000\cdot\frac{1}{13}}=$0.65
$ r=65\%$
