Pressure increase

[robvba]

1. The problem statement, all variables and given/known data
Suppose that the build-up of fatty tissue on the wall of an artery decreased the radius by 10%. By how much would the pressure provided by the heart have to be increased to maintain a constant blood flow?


2. Relevant equations
Poiseuille's equation


3. The attempt at a solution
52%?

[Redbelly98]

Yes.

[spikespeigel]

This was a while ago, but I hope someone can help me. I'm using continuity and get A1/A2 = 1.23, and using P = F/A, it looks like P1 = 1.23P2, which is a 23 percent increase. How do you get 52%? A little help? Thanks.