World's Shortest IQ Test Only Has Three Questions But 80 Percent Of People Fail It

Fancy yourself as cleverer than the average person...?

Written byHolly Barrow
Published on
Read time3 min read

Have you ever wanted to take an IQ test but never found the time to actually do it? If so, you're in luck. The world's shortest IQ test has just three questions so time isn't an issue, however your ability to pass it might be a different story...

The test has been around since 2005 and was first published by professor Shane Frederick in a research paper. It asks just three questions but a whopping 80% of people who attempt to crack it, fail it.

Professor Frederick had 3,000 participants take the test, with just 17% of those managing to get full marks. Apparently, the short quiz assesses your ability to process information slowly and rationally, rather than jumping to conclusions.

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Fancy yourself as a bit of a genius? Why not have a go...

1. A bat and a ball cost £1.10 in total. The bat costs £1 more than the ball. How much does the ball cost?

2. If it takes five machines five minutes to make five widgets, how long would it take 100 machines to make 100 widgets?

3. In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake?


Feeling confused? Don't worry - you're not the only one. Even students at Harvard and Yale - considered some of the most prestigious universities - struggled with this one.

Here are the answers so many struggle to reach: 5p, 5 minutes and 47 days.

If you're interested in how these answers come about, Presh Talwalkar explains them on his blog, Mind Your Decisions.

For the first question, Talkwalkar explains: "Say the ball costs X. Then the bat costs £1 more, so it is X + 1. So we have bat + ball = X + (X + 1) = 1.1 because together they cost $1.10. This means 2X + 1 = 1.1, then 2X = 0.1, so X = 0.05. This means the ball costs 5p and the bat costs £1.05."


For the second, he writes: "If it takes 5 machines 5 minutes to make 5 widgets, then it takes 1 machine 5 minutes to make 1 widget (each machine is making a widget in 5 minutes). If we have 100 machines working together, then each can make a widget in 5 minutes. So there will be 100 widgets in 5 minutes." And for the third, "Every day FORWARD the patch doubles in size. So every day BACKWARDS means the patch halves in size. So on day 47 the lake is half full."

Still going over your head? Well, if it's any consolation, IQ tests have been dubbed 'fundamentally flawed', with one study finding that using them alone to measure intelligence is a 'fallacy'.

We hope that softens the blow a little.

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