Professional and DIY IQ tests are popular because they offer a formula that allows you to compare yourself to other people and see how average (or above average) your intelligence is.

The cognitive reflection test (cathode ray tube) is dubbed the world’s shortest IQ test because it only has three questions. It assesses your ability to identify that a simple problem may actually be more difficult than it first appears. The faster you do it, the smarter you seem.

## Here are the three questions:

1. 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?

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

3. In a lake, there is a square of water lilies. 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?

## Here’s what a lot of people think:

1.10 cents

2.100 minutes

3. 24 days

When you’re ready, scroll down to find the correct answers and how to access them:

1. The bullet would actually cost 0.05 pence

If the ball costs X and the bat costs £ 1 more, then it will be:

X + £ 1

Therefore

Bat + ball = X + (X + 1) = 1.1

Thereby

2X + 1 = 1.1 and 2X = 0.1

X = 0.05

2. It would take 5 minutes to make 100 widgets.

Five machines can make five widgets in five minutes; therefore, a machine will also create a widget in five minutes.

Therefore, if we have 100 machines that all make widgets, they can make 100 widgets in five minutes.

3. It would take 47 days for the patch to cover half of the lake

If the patch doubles in size every day in the future, its size will decrease by half back. So, on day 47, the lake is half full.

In a investigation of nearly 3,500 people, 33 percent made a mistake of all three and 83 percent missed at least one.

While this IQ test has its flaws – its brevity and lack of variation in verbal and non-verbal reasoning – only 48% of the MIT students sampled were able to answer all three correctly.

How many have you done well? Tell us below

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