The correct answer is: [D]: " 7.2 units" .
_______________________________________________________
Step-by-step explanation:
________________________________________________________
Use the Pythagorean theorem:
a² + b² = c² ;
in which: "6 units" and "4 units" equal the lengths of the right angle (formed by the rectangle); and "c" is the length of the diagonal of the rectangle, or the "hypotenuse", of the right triangle formed by the rectangle; We wish to solve for "c" ;
_______________________________________________
6² + 4² = c² ; Solve for "c" ;
↔ c² = 6² + 4² ;
= (6*6) + (4*4) ;
= 36 + 16 ;
= 52 ;
c² = 52 ;
Take the "positive square root" of each side of the equation; to isolate "c" on one side of the equation; and to solve for "c" ;
√(c²) = √52 ;
c = √52 ;
At this point, we know the 7² = 49 ; 8² = 64 ; so, the answer is somewhere between "7" and "8" ; yet closer to "7" ; so among the answer choices given;
The correct answer is: [D]: " 7.2 units" .
_________________________________________
However, let use a calculator:
c = √52 = 7.2111025509279786 ; which rounds to "7.2" ;
which corresponds to:
___________________________________________
Answer choice: [C]: " 7.2 units" .
___________________________________________