Question

The interest on an investment varies directly as the rate of interest. If the interest is ​$48 when the interest rate is

5​%, find the interest when the rate is
7.9​%.

Answer 1

75.84

Explanation:

Interest(I) varies directly with the rate of interest(r) means there is some constant k such that I=k*r .

We are given when I=48 and r=0.05. Plugging this in the equation I=k*r will allow us to find the constant, k, no matter the I and/or r asked to use later in the problem.

Substituting I=48 and r=0.05 into I=k*r gives:

48=k*0.05

Divide both sides by 0.05:

48/0.05 =k

Putting left hand side into the calculator:

960=k

So no matter the I or r, the equation I=960*r holds.

So we are asked to find I if r=0.079 .

I=960*r with r=0.079 gives:

I=960(0.079)

I=75.84