<PRE><B>Question 304898</B>
 A runner’s heart rate in beats per minute is given by the formula Heart rate = 65 + 53 / (4t + 1) where t is the number of minutes after the start of a cool-down period. Find the runner’s heart rate in 10 minutes.
:
H.R. = 65 + {{{53/(4(10)+1)}}}
H.R. = 65 + {{{53/41}}}
H.R. = 65 + 1.3
H.R. = 66.3
:
When is the runner’s heart rate equal to 68 beats per minute?
65 + {{{53/(4t+1)}}} = 68
Subtract 65 from both sides
{{{53/(4t+1)}}} = 68 - 65
{{{53/(4t+1)}}} = 3
Multiply both sides (4t+1)
53 = 3(4t+1)
53 = 12t + 3
53 - 3 = 12t
50 = 12t
t = {{{50/12}}}
t = 4.2 minutes
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