Coronary heart disease can lead to the narrowing of coronary arteries, reducing blood flow to the heart muscle cells.
Table 1 shows how the percentage of the coronary artery's cross-sectional area that remains open affects the blood flow rate.
Table 1
| Cross-sectional area open (%) | Blood flow rate (cm3/min\text{cm}^3\text{/min}cm3/min) |
|---|---|
| 100 | 200 |
| 80 | 140 |
| 60 | 80 |
| 40 | 36 |
| 20 | 8 |
Describe the trend shown in Table 1 between the open cross-sectional area and the blood flow rate.
Calculate the percentage decrease in the blood flow rate when the open cross-sectional area of the artery is reduced from 100%100\%100% to 60%60\%60%. Show your working.
Assuming the change in blood flow rate is linear between an open area of 20%20\%20% and 40%40\%40%, estimate the blood flow rate when the open cross-sectional area is 30%30\%30%. Show your working.