Non-motoring > Can you pass the shortest IQ test? 3 questions. Miscellaneous
Thread Author: VxFan Replies: 10

 Can you pass the shortest IQ test? 3 questions. - VxFan

Thought to be the shortest IQ test in the world, the Cognitive Reflection Test consists of just three questions.

Here are the three questions:

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?


Now here are the most common answers, which are wrong:

1. 10 cents

2. 100 minutes

3. 24 days

===========================================

The correct answers are actually:

1. 5 cents

2. 5 minutes

3. 47 days

===========================================

Not sure how the answer to question one was 5 cents, not 10 cents?
Still wondering how question two was 5 minutes, not 100 minutes?
Helpfully, Presh Talwalkar, author of The Joy of Game Theory: An Introduction to Strategic Thinking explained how to work out the correct 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 five cents and the bat costs $1.05

2. If it takes five machines five minutes to make five widgets, then it takes one machine five minutes to make one widget (each machine is making a widget in five minutes). If we have 100 machines working together, then each can make a widget in five minutes. So there will be 100 widgets in five 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.

===========================================

Confused? yeah me too.
Last edited by: VxFan on Tue 26 Apr 22 at 14:24
 Can you pass the shortest IQ test? 3 questions. - sherlock47
Confused?

The only thing I am confused about is how people get them wrong!
Last edited by: sherlock47 on Tue 26 Apr 22 at 14:37
 Can you pass the shortest IQ test? 3 questions. - martin aston
I saw this last week. I tend to speed read so my only confusion was misreading the common answers as being the right answers. Then I was confused but otherwise I found them straightforward.

Nothing like a hard as some of the questions on “Only Connect” on BBC.
 Can you pass the shortest IQ test? 3 questions. - Ted

I used to enjoy Only Connect but I can't watch it now. The graphics are awful for someone whose eyesight is not up to scratch. The font colour has little contrast on the background. Don't get me going on 'the wall ' which jumps about all over the screen as you've just figured something out.

Victoria, however, is always worth watching !

The best detective show, Montelbano, is let down by it's sub-titles. White letters on white shirts and pale stone Sicilian buildings. Bah !

Ted
 Can you pass the shortest IQ test? 3 questions. - Lygonos
Took about 30 seconds to get the (right) answers - suspect it was a clickbait test?
 Can you pass the shortest IQ test? 3 questions. - sherlock47
Clickbait - I ignored when first seen on FB - pleased to see what it consisted of.
 Can you pass the shortest IQ test? 3 questions. - sooty123
I got the first one wrong and the others right. It took me a few goes to get my head around it, I guess the old RTFQ applies.
 Can you pass the shortest IQ test? 3 questions. - smokie
Same here Sooty
 Can you pass the shortest IQ test? 3 questions. - CGNorwich
Not really a test of intelligence, more a test of mathematical reasoning. You can be good at the latter and still not be very bright.. I’m sure, for example, that lots of people who voted for Boris are quite good at sums.
 Can you pass the shortest IQ test? 3 questions. - Fullchat
The bat and ball question came up on the Lee Mack's 1% Club show last night. My family were well impressed at the speed I answered it:))
 Can you pass the shortest IQ test? 3 questions. - zippy
>> The bat and ball question came up on the Lee Mack's 1% Club show last
>> night. My family were well impressed at the speed I answered it:))
>>

Same! Mrs Z was flabbergasted!
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