400
Recommended heart rates during exercise vary with age and physical condition. For healthy person doing moderate to intense exercise such as hiking, the inequality
0.5 (220 - a) <= R <= 0.9 (220 - a) gives a target range for the heart rate R (in beats per minutes) based on age a (in years). What is the target range for heart rates for a person 15 years old?
What is 102.5 <= R <= 184.5