Question 56817
0.7(220-a)<=R<=0.85(220-a) gives a target rate for pulse rate R (in beats per minute), based on age A in years). 
What is the target range for pulse rates for a person 35 years old? 
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If a=35,
0.7(220-35)<=R<=0.85(220-35)
129.5<=R<=157.25
If 140<=R<=170
then 220-a=140
a=80  (cousin is 80 yrs. old)

Cheers,
Stan H.