Could someone help me out on this?

Question

The simple interest I (in dollars) for a savings account is jointly proportional to the product of the time t (in years) and the principal P (in dollars). After nine months, the interest on a principal of $3500 is $91.88.

 

1. Find the constant of variation k.

2. Write an equation that relates I, t, and P.

3. What will the interest be after five years?

Answer 1

I = ktp

91.88 = k(0.75)(3500)

Solve for k. Then find I using p = 3500, t = 5, and the found value of k