Answer:
The constant of proportionality is option D i.e 5.
Step-by-step explanation:
Variation:
Variation problems involve fairly simple relationships or formulas, involving one variable being equal to one term. There are two types of variation i.e.
- Direct variation
- Inverse variation
Direct Variation:
Mathematical relationship between two variables that can be expressed by an equation in which one variable is equal to a constant times the other.
Example 
where, k is constant of proportionality.
The above given example is of Direct Variation
∴ y = 5 x
∴ k = 5 = constant of proportionality.
Inverse Variation:
Mathematical relationship between two variables which can be expressed by an equation in which the product of two variables is equal to a constant.
Example 
where, k is constant of proportionality.
Given :
Three points , P(4, 3, 4), Q(2, 1, 3), R(2, 7, 0) .
To Find :
The length of sides .
Given :
We know , length of two points P(x,y ,z) and Q(a,b,c) is given by :

Length of PQ :

Length of QR :
:
Length of RP :

Hence , this is the required solution .
Given:



To find:
The measure of angle MFZ.
Solution:
In triangles MFZ and PFZ,
(Right angle)
(Given)
(Common side)
(HL congruent postulate)
(CPCTC)




The value of x is 10.
The measure of angle MFZ is:



Therefore, the measure of angle MFZ is 19 degrees.