$\"\"$

Poiseuilles law states that the flux of the blood $\"\"$ .

Where $\"\"$ is the radius of the blood vessel and $\"\"$ is constant.

Consider $\"\"$ .

Apply derivative on each side.

$\"\"$ .

Relative error in flux $\"\"$ is $\"\"$ .

Substitute $\"\"$ and $\"\"$ in $\"\"$ .

$\"\"$

Therefore, relative error in flux is about four times the relative error in radius $\"\"$ .

$\"\"$

Percentage error in flux is $\"\"$ .

Here $\"\"$ is percentage error in radius $\"\"$ .

If there is 5% change in radius, then $\"\"$ .

Therefore, $\"\"$ .

Hence percentage error in flux is 20.

$\"\"$

Relative error in flux is about four times the relative error in radius $\"\"$ .

Percentage error in flux of the blood is 20.