1. Suppose a varies jointly with b and c and inversely with d and a = 400 when b = 16, c = 5, and d = 2. Write the equation that models the relationship.(Please show your work so I know how you got your answer and thanks in advance!)

1. The problem gives the following information: "a" varies jointly with "b" and "c" and inversely with "d". 

 2. You have that the values of "a", "b", "c" and "d" are:

 a = 400
 b = 16
 c = 5
 d = 2

 3. Keeping this on mind, you must calculate the constant of proportionality "k", as below:

 a=kbc/d

 3. When you clear "k", you have:

 k=ad/bc
 k=(400)(2)/(16)(5)
 k=10

 4. Therefore, you have:

 a=kbc/d
 a=10bc/d

 The answer is:

 a=10bc/d