Final answer:
Mandy's target heart rate for exercise at 80 percent intensity would be 160 beats per minute, which is calculated by taking 80 percent of her maximum heart rate determined by the formula 220 minus her age.
Step-by-step explanation:
Mandy is looking to find her target heart rate for exercise based on her age and a target heart rate objective of 80 percent. To calculate Mandy's maximum heart rate (MHR), we use the formula which estimates the MHR by starting with 220 beats per minute (bpm) and subtracting the person's age. In Mandy's case, Mandy is 20 years old, so her estimated maximum heart rate would be 220 - 20 = 200 bpm. To find her target heart rate at 80 percent intensity, we simply calculate 80 percent of her maximum heart rate, by multiplying her MHR by 0.80 (80 percent).
The calculation for Mandy's target heart rate at 80 percent intensity would therefore be 200 bpm × 0.80 = 160 bpm. This means that during exercise, Mandy should aim to maintain a heart rate of around 160 beats per minute to reach her desired intensity level for weight loss.