A principal of $5000 was invested in a savings account for 4 years. If the interest earned for the period was $400, what was the interest rate? [Hint: The formula for simple interest is I=Prt.]

I = PRT

400 = 5000 * R * 4
400 = 20,000R
0.02 = R

R = 2%

To find the interest rate, we can use the formula for simple interest: I = P * r * t, where:

- I is the interest earned,
- P is the principal (initial amount),
- r is the interest rate,
- t is the time in years.

In this case, we know:
- The principal (P) is $5000.
- The interest earned (I) is $400.
- The time (t) is 4 years.

We can rearrange the formula to solve for the interest rate (r):

r = I / (P * t)

Plugging in the values we have:

r = 400 / (5000 * 4)

To calculate this, divide 400 by the product of 5000 and 4:

r = 400 / 20000

Simplifying the division:

r = 0.02

The interest rate is 0.02, or 2%.