In this activity, students practice compound interest calculation – how to calculate one of the four variables. Before they start on the exercises, have the students recall what compound interest calculation is, its basic principle, and how it is calculated. Discuss the variables which are used in the formula, and what values these variables usually take in reality. Talk to the students about the use of compound interest calculation in everyday life and why it is important to know how to perform this calculation. As a follow-up activity, put the students in pairs and have them complete some practice exercises.

Give each pair of students eight jumbled up cards with questions on them (in Croatian). The worksheet with the cards can be created with the help of word processing software, for example MS Word. The students (in pairs) need to answer all the questions on their eight cards. Each question is linked to another in that the answer to one question provides the students with the information necessary to solve another question. The students will realize that they cannot answer the questions in random order and that they are expected to work out the order in which all the questions can be answered the quickest. Hand out cards with the QR code revealing the answers (in Croatian) to each pair of students when they have come up with all the answers. You can use the QR Stuff generator to create a QR code.

Monitor the students as they work and help as needed. At the end of the activity, you can use the online tool Tricider to discuss the questions and answers, the most common mistakes, and the best solution strategies.

Activities to support Special Education Needs students

Given the complexity of the questions in this activity, it is very important to provide students with disabilities with simple, brief and clear instructions and to check if they have understood these. If necessary, divide the activity into shorter stages and give the students instructions for each stage separately. For students with specific learning disabilities (dyscalculia, dyslexia, dyspraxia), it is necessary to adjust the number and the difficulty of the questions and give them enough time to complete them. Students with attention-deficit/hyperactivity disorder need to be introduced to the planned questions in advance, and these must be structured so that the students can successfully answer them. Generally, it is useful to provide most students with disabilities with a completed question to serve as an example when they answer similar questions.

Doing this activity should allow students to decide what interest rate and interest period are more favourable for a saver and to establish how the exponential function can be associated with everyday life.

Use the exponential function in compound interest calculation to discover how familiar students are with the procedure of interest calculation. You can use the Desmos activity titled Interest Rate (this is an example of this activity in the Desmos tool in Croatian). The students can access the activity by entering the class code which the teacher can generate by logging into Desmos, where they can monitor the activity of each student. As they fill in the table, the students will discover that it is more favourable for a saver to have as short an interest period as possible (assuming the interest rate is the same). They are introduced to the concepts of a nominal, relative and conforming interest rate. After the activity, discuss the use of these terms with students to give them an opportunity to think critically about the conditions which banks offer.

Activities to support Special Education Needs students

This activity is highly relevant to everyday needs, particularly to the students’ future lives as it develops the foundations of financial literacy. Therefore, it is important for students with specific learning disabilities and attention-deficit/hyperactivity disorder to be supported in a variety of ways so as to have them acquire knowledge which they will find of utmost importance. The terms nominal, relative and conforming interest rate should be further explained so that students can understand them well. It is advisable to use small numbers at first, in order for the students to learn the stages of the procedure. Students can have a glossary in their notebook to help them recall what each term means. Instructions for tool use, support and step-by-step guidance through the activity, as well as additional clarification constitute some of the possible support procedures, which are described in more detail in the Didactic-Methodical Guidelines for Natural Sciences and Mathematics for Students with Disabilities.

Ask the students if they save money and what they know about savings. Which conditions do banks offer? Is it worth saving your money in a bank?

Divide students into groups and assign a bank to each group. Ask them to do the following task:

Find out what the annual interest rate is for fixed-term savings in Croatian kuna at the bank you have been assigned. Determine the amount you want to place on time deposit (joint savings) until the 21st birthday of the youngest member of the group. How much interest would you receive if the interest were compounded a) annually, b) quarterly, c) monthly?

Choose the most favourable compounding interest option from those your assigned bank offers and answer the questions: a) How long would you have to wait for the fixed-term deposit amount to double? b) How long would you have to wait to be able to withdraw HRK 20,000?

Ask the groups to find the information they need on the website of the bank they have been assigned. Help them choose the type of interest they will need.

Ask the students to create an infographic using Piktochart and use it to present the results of their research to the rest of the class.

After the presentations, discuss the conditions offered by different banks and ask the students again if it is worth saving your money at a bank. Are the results what the students expected?

Comment on why the period required for the fixed-term deposit amount to double does not depend on the deposit amount.

Activities to support Special Education Needs students

In this activity, most of the support to students with disabilities can be provided by other students in their group, e.g. they can read the information on the bank websites to students with visual impairments and dyslexic students. If necessary, the text can be read several times, and students may write down important data to create a personalised flowchart. It is also important to provide step-by-step guidance, i.e. clear instructions before each new stage in the activity. Based on their prior knowledge and abilities, decide if students with disabilities should complete the whole activity or just those parts related to basic knowledge (e.g. calculating the annual interest and crediting it to the principal).

Talk to the students about loans. What loan terms do the students know? Is anyone close to them paying off a loan? Why do people take out loans? In the long run, is it better to take out a loan or save up the money you need?

Explain to the students that the annuity (periodic payment amount) consists of the repayment quota (the loan payment part) and the interest (the part which covers the fee for using the funds transferred). The interest is calculated on the remainder of the debt. After each payment is made, the debt is reduced by the repayment quota.

Loans are most commonly repaid either in equal annuities or equal payment quotas. An overview of loan repayment is given in a repayment table (in Croatian).

Ask the students to find someone they know who is paying off a loan. Have them collect information about the loan amount, interest rate and repayment period. Ask them to work in pairs and use the spreadsheet software Excel Online to create repayment tables for the two repayment methods – in equal annuities and in equal repayment quotas, as in the example (in Croatian). To calculate an annuity in the case of a loan repayment in equal annuities, use the Excel function called PMT (you can show advanced students how the amount is determined mathematically; they need to be familiar with the sum of a geometric series). Default data is used to calculate other data in the tables. Once they have created the repayment table, ask the students to determine the total amount of interest to be paid in both cases.

As they compare the tables, ask them to consider which method is better and why. Have them share their thoughts via Edmodo. Have the students comment on their findings with the person they initially asked for information about their loan.

Activities to support Special Education Needs students

If they are encouraged to participate in the introductory discussion, students with disabilities will be motivated to join in. When you have explained the concepts of annuity, repayment quota and interest, you need to check if the students understand them, and if they do not, the concepts should be explained once again in simple terms and small numbers. If the tables or their content are too challenging for students with specific learning disabilities, they can be summarised and given to the students in the form of a template, to be used as a reminder. Only when you are confident the students understand the basic concepts, can they be involved in further individual activities and pairwork. Students need to be given detailed instructions on the use of digital tools, and you should check if the students understand these. Adjust the method of loan repayment calculation to the students' prior knowledge. Visually impaired students who can’t use digital tools can use a calculator and record the results in a way they find preferable.

For students who want to know more

Encourage students to browse online and find out the following:

1. the difference between decursive and the anticipatory interest calculation
2. the definition of prenumerando and postnumerando periodic payments

Encourage them to visit several banks and ask which method is used more often, in which cases and why. They can use these findings to build a website with Tackk, a tool which allows users to easily add varied content (text, images, videos, links, geolocation, etc.). Have them share their work with the rest of the class and comment on it.