problem:
Mary will buy a new kitchen.
Therefore she has to take up a loan of € 8 000, which she wants to repay after 8 month.
The bank wants € 240,- interest.
What is the interest rate?
answer:
1. step: given/wanted
capital: € 8 000,-
interest: € 240,-
time: 8 month
wanted: interest rate in % ?
2. step: calculate
Tom:
i = interest c = capital ir = interest rate m = months
i = c * ir * m
1 200
240 = 8 000 * ir * 8
1200
240 = 8 000 * ir * 8 / * 1 200
1 200
288 000 = 64 000 * ir / : 64 000
ir = 4,5%
3. step: answer
The interest rate is 4,5%.