Geometry study guide

Question

Find the perimeter of a quadrilateral with vertices at C (−2, 4), D (−3, 1), E (1, 0), and F (−1, 2). Round your answer to the nearest hundredth when necessary.

10 units

10.77 units

11.52 units

12.45 units

Answer 1

Definitely plot as the points may not be in the correct order for the quadrilateral (should be, but problem makers get strange ideas) and the way to get errors right is to never round until the end of your calculation (when you are displaying the answer). The usual rule is to not use rounded values in further calculations. In this case, this is not causing the error - the answer choice D is just not quite right.

Answer 2

-2,4

-3,1

1,0

-1,2

it may help to graph the points

use the distance formula or the Pythagorean Theorem to calculate 4 distances

d=sqr((x1-x2)^2 + (y1-y^2)^2)

then sum them

(-2,4) to (-3,1) = square root of (4-1)^2 + (-3+2)^2 = sqr(3^2 +1^2) = sqr10

other 3 sides are sqr17, sqr5 and 2sqr2

Perimeter = sqr10+sqr17+sqr5+sqr8 = about 3.16+4.12+2.24+2.83 = about 12.35

rounding approximations may throw the last digits off a little

D 12.45 is best answer