Question

Solve the following variation problem

The interest on an investment varies directly as the rate of interest.
If the interest is $49 when the interest rate is
4%, find the interest when the rate is
7.7%

Answer 1

$94.325

Explanation:

Given interest (I) varies directly as rate of interest (R) then the equation relating them is

I = kR ← k is the constant of variation

To find k use the condition I = 49 when R = 4 , then

49 = 4k ( divide both sides by 4 )

12.25 = k

I = 12.25R ← equation of variation

When R = 7.7 , then

I = 12.25 × 7.7 = $94.325