Interest, loans and savings: watch it solved step by step

Simple and compound interest, depreciation, a loan's monthly payment and a savings annuity, each checked a second way. Level: GCSE / University. Type any problem of this kind and the Lab works it out and animates every move, with a plain-words explanation of why.

Worked example: 1200 at 5% for 4 years simple

1. Understanding the problem. Simple interest is paid only on the original amount, the same every year.
2. The formula. Interest = principal × rate × time.
3. Substitute. Write the rate as a decimal (÷ 100).
4. Interest earned. Multiply to find the answer.
5. Total amount. Add the interest to the original amount.
6. Check. Each year earns the same interest, so one year times the number of years should match.

Answer: 1,440.00 (interest 240.00)

Practise interest, loans and savings with problems the Lab marks for you.