Proportionality and percentages
Banking interest
The profit that we obtain when we lend our money is called interest. This profit is directly proportional to the time that the loan lasts and to the amount that we lent. The percentage of profit is called interest rate. Then we have a compound rule of three:
Example 1: A bank offers an interest rate of 4%. What interest will we obtain if we deposit 750€ for 3 years?
We obtain 90 €
Example 2: How much money will I have to pay back to the bank if it lends me 2000€ at 5% for 4 years?
I'll have to pay back 2400 €
Exercises:
1.- What interest will I obtain if we deposit 1500 € for 10 years at 3%?
2.- How much money will I have to deposit in a bank for 5 years at 5% to obtain 5000€ of interest?
Solutions: 1) 450 €; 2) 20000 €
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