SAT Mathematics Practice Test 4

The equation that models the normal systolic blood pressure, in millimeters of mercury, for a male x years old,$\mathit{p}=\frac{\mathit{x}+220}{2}$ ,can be rewritten as $\mathit{P}=\frac{1}{2}\mathit{x}+110$ For each increase of 1 yearin age, the value of x increases by 1; hence, P becomes $\frac{1}{2}\left(\mathit{x}+1\right)+110=\left(\frac{1}{2}\mathit{x}+110\right)+\frac{1}{2}$.That is, P increases by $\frac{1}{2}$ millimeter of mercury. Either the fraction $\frac{1}{2}$ or its decimal equivalent, .5, may be gridded as the correct answer.