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Calculating Simple Interest

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Aligned To Common Core Standard:

Grade 7 Ratios - 7.RP.A.3

How to Calculate Interest - When it comes to solving money problems, calculating interest is one of the trickiest types of exercises that can confuse the students. It is crucial to develop strong skills in solving money problems as we have to incorporate these concepts into our day to day operations. There are two types of commonly explored forms of interest these include simple and compound. When you borrow money, you have to pay the fee in the form interest which is equal to some percent of the amount you borrowed. This is the benefit that the lender receives for giving you access to money. The simple form is when you pay the same amount of interest every year. You can calculate this by using a simple formula; simple= principal amont borrowed × rate × time or I =Pr t. All you need to know is the principal amount borrowed, the rate that is set by a lender, and the time you have borrowed the money for. Compound forms are where things get a bit complex. When you consider compound forms, the new end cost for every year adds together. Meaning that the overall principal grows much quicker and contributes to the future principal amount. For example, you borrow money for two years. You can use the simple formula to calculate the cost for the first year. For the next year, the interest of the first year will add to the principal amount, and then the cost will be calculated on the new amount. These worksheets help students learn the concept of financial interest and how to determine it.

Printable Worksheets And Lessons

Simple Interest Practice Sheets

Use the formula to help you find the simple interest and total cost of the following problems.

  • Independent Practice 1 - This sheet will help you learn to calculate both the interest and total cost.
  • Independent Practice 2 - Determine the amount of simple interest you would incur in the following money borrowing scenarios. There are several different problems that focus all on the same skill.
  • Independent Practice 3 - Brady decides to purchase a trip to London. After the airfare, lodging, and meals are calculated it will cost $3,250 for a weeklong stay. Brady charges the cost of the trip on a credit card with an interest rate of 13.5%. If it takes Brady 3 years to pay back the cost of the trip, how much will Brady pay in total?

Homework Sheets

You will use a wide range of skills to complete all of the homework.

  • Homework 1 - This homework sheet covers the major skills in a very matter of fact approach.
  • Homework 2 - We are solely focused on the increased costs of taking out a loan.
  • Homework 3 - Halley and Jason bought a new home for $185,000. They take out a loan from Astar Bank to pay for their home. The terms of the loan are 6.5% for 30 years. If the pay the loan off over the 30 years, how much interest will they have paid to Astar Bank?


Time to see how well you understand the concepts that are presented in this topic.

  • Quiz 1 - Who doesn't what to be able to calculate this value?
  • Quiz 2 - I learned this skill in school, but until you have taken out your first loan it doesn't really sink in how much each percentage point means.
  • Quiz 3 - Mike buys a Certificate of Deposit (CD) for $45,000.00. The terms of the CD are 4.55% for 12 years. When the CD expires how much total money will Mike receive?

Why Is Understanding the Concept of Interest So Important?

This concept is glanced over in most math classes, but it can have a huge impact on your life in adulthood. If you are lucky, you will get an opportunity to take a personal finance class in High School. If you get the opportunity, I implore you to take it and pay the utmost attention to detail. This principal is the foundation of the American economic system. It has the biggest influence of how much money you will owe in a borrowing situation and how much return you will get on your savings. I will not go into much detail on the different types of rates that help money to flow through the banking system, but it is substantial, to say the least. While most people will understand savings accounts rates and how they work, borrowing is an entirely different animal. When people take out their first personal loan, they are simply happy to have someone else pay for items that they really want. You need to realize that they are not giving you the money because they have to. You are purchasing a financial product that is aimed to make the lender more money. Like any product lenders have competition to get you interested in theirs. You should spend your time reviewing the terms and understand which best suits your situation. When it comes to mortgages (loans for purchasing homes) you have tons of options and you need to take your time to find a loan that works for you. I would encourage you to do your research. Many people think that they need to take out loans from local banks and lenders. If you do a quick Internet search, you will quickly realize that have literally hundreds of options. Making the best decision will greatly help you. Take my first home loan as an example. I had no idea what I was doing and took whatever loan my real estate agent advised. About a year later I realized that I paid 1.5% more than others that were available at the time. Over the life of 30-year loan, that was a $75,000 mistake. Do not make my mistake, do your research.