Mixture problem help solve

Question

Lisa has a total college account of $120,000. $50,000 of this is an account that pays 3.35% interest. What interest rate would she need on the rest in order to get $6,000 per year in interest all together?

Answer 1

If we call the interest rate r, then...

 

.0335(50,000) + 70,000t = 6000

1675 + 70,000t = 6000

70,000t = 4325

t = .0168 = 6.18%

 

Hope this helps!

Answer 2

3.35% simple rate of interest on $50,000 earns [($50,000*3.35)/100]=$1675 in a year which is a part of $6000 that Lisa need per year all together

Hence the rest of the interest should be ($6,000-$1,675)=$4,325

The remaining capital = ($120,000-$50,000)=$70,000

Thus $70,000 can earn $4,325 at the rate of simple interest = [($4,325/$70,000)*100] ≈ 6.18 

 

Therefore, Lisa would need on the rest, i.e., $70,000, 6.18 % interest rate in order to get $6,000 per year in interest all together.

 

NOTE: I calculated with simple rate of interest instead of compound interest rate because of the available data. The frequency of compounding was required to calculate compound interest rate, which has no mention in the question.