Explanation for Question 25 From the Math (Calc) Section on the 2019 March Sat
Question 25 says the diagram above represents Edward T Hall's concept 2 of space surrounding the person defined by four non overlapping regions. 3 Intimate space is the region inside the circle of radius. 4 One foot personal space is the region within a circle of radius four feet, 5 but outside intimate space, social space is the region within a circle 6 of radius, 12 feet, but outside personal space and public space is the region 7 within a circle of radius, 25 feet, 8 but outside social space, what does the area in square feet of the shaded 9 region representing a person's social space? 10 So to find out the area of the shaded region here, 11 we're going to have to find out the area of this circle. 12 And so track the area of the smaller circle of personal space. 13 So personal space has a radius of four feet. 14 So I'm going to mark that here. So from here to here is four 15 and social space has a radius of 12 16 feet. So that means from the center of the circle to here is 12. 17 So we're going to use the circle area equation, 18 PI R squared. And we're going to do that equation and plug in 19 12 minus that equation plugging in four. 20 So 12 squared is 144, 21 so 144 PI minus four squared PI, 22 which is 16 PI. 23 And what does that give us? That gives us 1 28 PI. 24 And so we know that the answer is B.