The challenge is to find out the Odd Number “16” in this Numerical Optical Illusion. Can you prove you have an IQ level of 169 or higher with 20/20 vision?

Only 1% can spot the hidden odd number in this ‘421’ numerical optical illusion. Test your observation, IQ, and Hawk–Eye vision in this fun brain teaser.

This optical illusion puzzle is putting observation skills to the test, challenging readers to find the hidden 4155 among dozens of 4165s in under 10 seconds.

Optical-illusion challenge: A 13×11 grid filled with “858” plays a trick on the eyes - only one box is different. Can you find the odd number before time runs out?

The challenge is simple yet deceptive, find the odd number out without letting your eyes trick you? Illusions such as this, trick our visual field.

Find the 2o2 in the grid of 202s in just 12 seconds. Only 1 in 10 people can complete this challenge. Optical illusions are spreading like wildfire on the internet.

How does Luhn’s algorithm know when your fingers fumble? Every digit in a credit card number contributes a one-digit number to the final sum in the algorithm.

The mean is the mathematical average of two or more numbers. Find out how investors and economists use the mean to track performance.

Defensive Line 101: What to know about d-line positions, fronts, techniques, terms and more We'll tackle several other positions this offseason and we'll refer back to these pieces once we begin ...