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Mathematics · Money · A primer

Compound interest, from scratch

This is the money in your bank account and the money on a loan. No formula until you have already worked it out by hand.

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Short, simple wording. Tap “Full” for the richer text and extra examples.

1The whole idea

one sentence

Money you earn as interest starts earning interest of its own. So next year you earn interest on a bigger pile than you had this year — and the pile keeps getting bigger.

That is the only difference from simple interest. With simple interest you always earn on the original amount. With compound interest you earn on everything you have, including what you earned last time.

Quick check
1.

After one year, €1,000 at 10% has grown to €1,100. In year two, the 10% is taken on…

2.

€1,000 at 10% for one year — how much interest is that?

3.

What is the ONE difference between simple and compound interest?

2Watch it happen, year by year

First get the quick-check questions in the section above right — then this one opens.

3Do it by hand once

First get the quick-check questions in the section above right — then this one opens.

4The shortcut

First get the quick-check questions in the section above right — then this one opens.

5Your turn

First get every section's quick-check right above — then the practice, guided and test questions open.

6Final test

First work through every section above — then the final test opens.