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Heart Disease As age increases, so does the likelihood of coronary heart disease (CHD). The fraction of people $$x$$ years old with some $$CHD$$ is modeled by $$f ( x ) = \frac { 0.9 } { 1 + 271 e ^ { - 0.122 x } }$$
$$\left. \begin{array} { l } { \text { 57. (a) } 0.065 ; 0.82 \text { ; Among people age } 25,6.5 \% \text { have } } \\ { \text { some } CHD \text { , while among people age } 65,82 \% \text { have some } } \\ { \text { CHD. (b) } 48 yr } \end{array} \right.$$