If $r + \frac{64}{r}= 16$, then the value of $r^4 +\frac{1}{r^3}$ is __________.

$4096\frac{1}{512}$

If $r + \frac{64}{r}= 16$,

then the value of $r^4 +\frac{1}{r^3}$ = ?

If $r + \frac{64}{r}= 16$,

Put the value of r = 8 ( This value will satisfy the given equation)

$8^4 +\frac{1}{8^3}$ = $4096 +\frac{1}{512}$  = $4096\frac{1}{512}$