Answer
Please see the work below.
Work Step by Step
We know that according to law of conservation of energy
$\frac{1}{2}mv^2=\frac{1}{2}kx^2$
This simplifies to:
$v=\sqrt{\frac{K}{m}}x$
We plug in the known values to obtain:
$v=\sqrt{\frac{40000}{10000}}(25)=50\frac{m}{s} = 180 \frac{km}{h}$
