A major artery with a cross-sectional area of 1.00cm2 branches into 18 smaller arteries, each with an average cross-sectional area of 0.400cm2. By what factor is the average velocity of the blood reduced when it passes into these branches

The velocity in the smaller arteries will be reduced by a factor of 0.139

Explanation:

The flow rate of blood is going to stay the same when it is transferred from the major artery to the smaller ones.

flow rate = Velocity * Area

Since the flow rate remains constant, we have:

Flow rate in major artery = combined flow rate in smaller arteries

Velocity in Major artery * 1.00 = Velocity in smaller artery * (0.4 * 18)

Thus, the velocity in the smaller arteries will be reduced by a factor of 0.139

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

wavelength variability is the right one