Answer:
Option A is correct
Value of A is, 189
Step-by-step explanation:
Joint variation states:
A varies jointly as b and c.
⇒[tex]A \propto b[/tex] and [tex]A \propto c[/tex]
⇒[tex]A \propto bc[/tex]
then the equation is in the form of:
[tex]A = k \cdot bc[/tex]
where, k is the constant of variation.
As per the statement:
A varies jointly as b and c.
⇒[tex]A = k \cdot bc[/tex] ....[1]
To find A .
Substitute the given values b = 7 , c = 9 and k = 3 in [1]
then;
[tex]A = 3 \cdot 7 \cdot 9 = 21 \cdot 9 = 189[/tex]
Therefore, the value of A is, 189
