# World’s shortest IQ test with only three questions

If you want to put your intelligence to the test during lockdown we have the perfect quiz for you.

The world's shortest IQ test is made up of just three maths questions and shouldn't take too long to complete.

But don't be fooled, this test is just as tough as the rest.

Originally published in 2005 by Professor Shane Federick, as part of a research paper named the Cognitive Reflection Test, it has resurfaced online with those keen to find out their intelligence, reports The Mirror.

The study had 3,000 participants from a range of educational backgrounds, including some Harvard and Yale University students.

However, only 17 per cent managed to bag a three out of three score, resulting in 83 per cent of people failing. But how will you fare?

Speaking about the test, Professor Frederick, said: "The three items on the CRT are 'easy' in the sense that their solution is easily understood when explained, yet reaching the correct answer often requires the suppression of an erroneous answer that springs 'impulsively' to mind."

Below you will find the questions, answers and theory behind them.

Question -1 of 3 Score -0 of 0 A bat and a ball cost \$1.10 in total. The bat costs \$1.00 more than the ball. How much does the ball cost?

• 5 cents
• 10 cents
• 15 cents

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The paper quotes Jensen, 1998, and says: "People with higher cognitive ability (or "IQ") differ from those with lower cognitive ability in a variety of important and unimportant ways.

"On average, they live longer, earn more, have larger working memories, faster reaction times and are more susceptible to visual illusions."

If you're as confused as we are, thankfully, Presh Talwalkar, from The Joy of Game Theory: An Introduction to Strategic Thinking, explains the answers on his blog.

1. 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 5 cents and the bat costs \$1.05

2. If it takes five machines 5 minutes to make five widgets, then it takes one machine 5 minutes to make one 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.

3. 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.

These are the three most common answers that people guess – but they are actually incorrect.

1. 10 cents

2. 100 minutes

3. 24 days