Interest Rate math problem

[coolwithjen2000]

Ms. Suarez wants to earn $150 in interest over a 3-year period from a savings account. The principal she must deposit varies inversely with the interest rate of the account. If the interest rate is 0.08, she must deposit $625. If the interest rate is 0.064, how much must she deposit?





Thank you for helping me

 

[Denis]

The 150 is calculated this way: 625 * .08 * 3 = 150

If rate .064:
D * .064 * 3 = 150

Solve for D. OK?

 

[tkhunny]

Ms. Suarez wants to earn $150 in interest over a 3-year period from a savings account. The principal she must deposit varies inversely with the interest rate of the account. If the interest rate is 0.08, she must deposit $625. If the interest rate is 0.064, how much must she deposit?

What an odd question. Inverse variation?

"The principal she must deposit varies inversely with the interest rate of the account"

This means P = k/i, where P = principal amount, i = interest rate, and k = constant of proportionality.

"If the interest rate is 0.08, she must deposit $625."

This means 625 = k/0.08 -- Solving for k gives k = 625*0.08 = 50

"the interest rate is 0.064, how much must she deposit"

This means P = 50/0.064 and calculate P.