The 30-Second IQ Test

Publish Date
Thursday, 12 October 2017, 11:58AM

The Cognitive Reflection Test, is the world's shortest IQ assessment and contains just three questions, which appear relatively simple at first glance. 

Published in 2005 in the Journal of Economic Perspectives, the test has resurfaced online following US President Donald Trump's challenge to Secretary of State, Rex Tillerson to 'compare IQ tests' after reports the latter called the president 'a moron'.

The rapid test would be an ideal option for two such busy men to settle their dispute as it contains just three questions. 

However, the test is in fact a lot more tricky than it looks and the proof of a high intellect is realising this and working out the answers accordingly. 

Scroll down to take the test and find out if you have above average intelligence.




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 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? 




1. 10 cents

2. 100 minutes

3. 24 days 




Question 1

If the ball costs X, and the bat costs $1 more, then the cost is X+$1

Therefore Bat+ball=X + (X+1) =1.10

This means 2X+1=1.1, and 2X=0.1 and X= 0.05

Correct answer: 5 cents (with the bat costing $1.05)

Question 2

If five machines can make five widgets in five minutes, one machine will make one widget in five minutes.

 So if 100 widgets are all making widgets, they can make 100 in five minutes.

Correct answer: 5 minutes 

Question 3 

If the lily patch is covering the pond fully on day 48, and it's doubled in size that means you only have to go back one day to when it was covering half the pond. So on day 47, the lake is half full.

Correct answer: 47 days  


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