2nd April 2026
Earlier this week, we shared a World Maths Day (25th March) brain-teaser designed to test financial instincts and everyday number sense.
THE BRAIN-TEASER
You receive:
- £1,000,000 today, or
- 1p today that doubles every day for 30 days, or
- £100,000 every day for 30 days
Which gets you more?
The responses highlighted something important about how our intuitions can get in the way when it comes to our finances.
35%, over a third of voters, chose £100,000 every day for 30 days. This option offers a steady and substantial increase, making it feel like a strong and reliable choice.
18% of people chose £1,000,000 today, which is perhaps the most intuitive option. It’s a large, immediate reward, and doesn’t require any waiting or uncertainty.
47% of people chose 1p doubling every day for 30 days, which may appear modest at first glance, but follows a very different pattern of growth. Perhaps surprisingly, choosing 1p and having that amount double every day for 30 days yields the highest total.
What this demonstrates is the difference between linear growth (adding the same amount each time) and exponential growth (where amounts increase more rapidly over time). Exponential growth starts slowly, which makes it easy to underestimate, but over time, it can become significantly larger than expected, as we’ve seen in the doubling 1p example.
It also reflects a common tendency known as present bias, where we naturally favour options that feel immediate, certain or easy to understand, even if longer-term options may deliver greater value.
While this is a simple puzzle, the underlying idea plays an important role in everyday finances. Concepts like compound growth underpin savings, interest and long-term financial planning, yet they can be easy to overlook because their impact isn’t always obvious at the start.
As this puzzle shows, growth isn’t always obvious at the start, and numbers aren’t always intuitive. At Earl Shilton Building Society, we believe building confidence with these ideas is an important part of financial literacy. Making numeracy more accessible helps people better understand how their money can grow over time, supporting more informed decisions for the future.
In light of this, we help members take a longer-term view, supporting them in building savings gradually and working towards their financial goals.