Does a rhombus have perpendicular line segments

A rhombus is a geometric figure that lies in a plane. It is defined as a quadrilateral all of whose sides are congruent. It is a special type of parallelogram, and its properties (aside from those properties of parallelograms) include:

Its diagonals divide the figure into 4 congruent triangles.

Its diagonals are perpendicular bisectors of eachother.

If all of a rhombus' angles are right angles, then the rhombus is a square.

A. 45/100 reduced = 9/20
(divided 45 and 100 by 5 to get 9 and 20)

B. she has finished 27 problems, which is 45% of her homework. In other words
45% of the total problems = 27 
if we use X to represent the total amount of problems, then: 
45% X = 27
we solved in part A for 45%, which is 9/20, so then:
9/20 x = 27 
now all that's left is to solve for x
first multiply both sides by 20
9x = 540
now divide both sides by 9
x = 60
the total amount of problems, or the number of problems she was assigned is 60 problems. 

C. If the total amount of problems she had to do was 60, and she has already done 27, then 
60 - 27 = the amount of problems she has left
33 = the amount of problems she has left

she has 33 problems left to do.