The Cognitive Reflection Test (CRT) is the world’s shortest adult (16+) intelligence test.
Duration: 5 minutes
Scoring
Scoring range: 0–3
Threshold score: 2
83% of people missed at least one of the questions.
Frederick gave the CRT to students at nine American colleges, and the results track pretty closely with how students from those colleges would rank on more traditional intelligence tests.
Students from the Massachusetts Institute of Technology—perhaps the brainiest college in the world—averaged 2.18 correct answers out of three. Students at Carnegie Mellon University in Pittsburgh, another extraordinarily elite institution, averaged 1.51 right answers out of three. Harvard students scored 1.43; the University of Michigan, Ann Arbor, 1.18; and the University of Toledo 0.57. ~ from David and Goliath by Malcolm Gladwell.
Answers
(1) 5 cents (not 10)
(2) 5 minutes (not 100)
(3) 47 days (not 24)
Extra explanation
(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? _____ cents
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 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets? _____ minutes
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.
(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? _____ days
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.