Thirty minutes of exercise per day can reduce your blood pressure. Which of the following is a guideline for establishing causal
ity? a) Look for evidence that smaller amounts of exercise produces a reduction in blood pressure.
b) Check if lower blood pressure is present or absent when exercise is present or absent
c) Perform a randomized, controlled experiment.
d) Control the number of minutes of exercise and blood pressure to get the same results.
It's 21 square units. If you map it on a complex plane (x-axis is real numbers, y-axis is imaginary numbers) you'll see that the sides of the rectangle is 3 and 7 which multiply to 21.
