A penny doubled
Two choices. Tap the one that ends up bigger.
Interest rates are examples, not a forecast.
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What the game is
Each game has five rounds. The first is the classic puzzle: a million pounds today, or a penny that doubles every day for 30 days. The other four compare ways of saving, such as a lump sum now against a smaller amount every month, or starting at 25 against starting at 35.
After each choice the game shows what both options are worth at the end and draws both on a small chart, so you can see where one overtakes the other.
Why the answers surprise people
Growth that builds on itself starts slowly and then speeds up. After three weeks of doubling, the penny is worth only about ten thousand pounds. The last few doublings are where almost all of the money appears.
Savings with compound interest follow the same pattern, only more gently. Interest is added to the balance, and next time interest is worked out on the bigger balance. Time matters as much as the rate, which is why the rounds about starting early often go against people's first guess.
What the game assumes
The interest rates in the game are examples, not a forecast. Real rates change, and no account is guaranteed to pay them. The sums add interest monthly, take no tax off and do not allow for rising prices.
To try your own figures, use the compound interest calculator. The savings challenge calculator sets out the 1p a day and 52-week challenges, and the inflation calculator shows what money from past years is worth now.
How to play
- Read both choices.
- Tap the one you think is worth more at the end.
- Look at the two end values and the chart, then press "Next".
- After five rounds, copy your score to share it.
The game stores nothing on your device, so each visit starts fresh.