New Delhi, Aug. 19 -- The popularity of optical illusions is on a meteoric rise on the internet. As a result, these brain teasers are getting harder on a daily basis. If you prefer challenges, we have an appropriate optical illusion to test your cognitive agility. All you must do is find 84 from this grid of 48s within 10 seconds of your time.

It is fascinating how these brain teasers can sharpen a person's IQ and help them think outside the box. While most of these optical illusions initially appear child's play, they can put even the smartest ones in a fix.

At first glance, there is a grid of the digit 48. Somewhere hidden in the grid is 84, the digit reversal of 48. The challenge is to locate 84 in less than 10 seconds of your time....