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The target heart rate for moderate exercise is $50\%$ to $70\%$ of maximum heart rate. We can use the expression $\frac{p}{100}(220-a)$ to represent a person’s target heart rate when their target rate is $p\%$ of their maximum heart rate, and they are $a$ years old.

Determine the target heart rate at the $53\%$ level for moderate exercise for someone who is $56$ years old.

At the $53\%$ level, the target heart rate for moderate exercise for someone who is $56$ years old is

beats per minute.

Solution

$\begin{aligned} \frac{p}{100}(220-a)\amp=\frac{\substitute{53}}{100}(220-\substitute{56})\\ \amp=\frac{53}{100}(164)\\ \amp=\frac{53}{25}(41)\\ \amp=86.92 \end{aligned}$

At the $53\%$ level, the target heart rate for moderate exercise for someone who is $56$ years old is $86.92$ beats per minute.