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Loans & investment. Simple Interest. Simple Interest. Example 1. I purchase a car valued at $12 000 with a 30% deposit and the balance paid off with monthly instalments over 2 years at a rate of 8.5% p.a. Find. (a) The amount of the deposit. (b) The balance owing.
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Loans & investment Simple Interest
Simple Interest Example 1 I purchase a car valued at $12 000 with a 30% deposit and the balance paid off with monthly instalments over 2 years at a rate of 8.5% p.a. Find (a) The amount of the deposit (b) The balance owing (c) The interest on this balance (d) The total to be repaid (e) The amount of each monthly instalment
(a) The amount of the deposit 30% of $12000 = 0.3 x 12000 = $3600 (b) The balance owing = original amount – deposit = 12000 - 3600 = $8400 (c) The interest on this balance = PRT/100 = 8400 x 8.5 x 2 / 100 = $1428
(d) The total to be repaid = principal + interest = $8400 + 1428 = $9828 (e) The amount of each monthly instalment = $9828 ÷ 24 = $409.50
Example 2 I want to buy a sound system valued at $12000. I decide to pay $3000 deposit, then get a loan to pay the remainder off over 3 years. My monthly instalments (repayments) are $313.75. Find (a) The amount that I have to borrow (b) The total that I repay in instalments (c) The amount of interest that I pay (d) The effective interest rate per annum, i.e. the simple interest rate that I am paying
(a) The amount that I have to borrow = 12000 - 3000 = $9000 (b) The total that I repay in instalments = $313.75 x 36 = $11295 (c) The amount of interest that I pay = Total of all instalments - principal = $11295 - 9000 = $2295
I = 2295 P = 9000 T = 3 R = 100 I / PT (d) The effective interest rate per annum, i.e. the simple interest rate that I am paying For this we use the “R” version of the simple interest formula, i.e. R = (100 x 2295) / (9000 x 3) R = 8.5 The annual effective interest rate is therefore 8.5% p.a.