If (a) varies jointly as b and c, and a= -10, when b= 12 and c= 2 , find (a) when b=8 and c= 1/2

Question

When (a) is in parentheses that means that it is a variable not like the word “a” , just for clarification

Answer 1

Since a varies jointly as b and c, a = kbc, for some constant, k.

Since a = -10 when b = 12 and c = 2, we have -10 = k(12)(2). So k = -10/24 = -5/12.

a = (-5/12)bc

So, when b = 8 and c = 1/2, a = (-5/12)(8)(1/2) = -5/3.