Brain teasers and puzzles have been around for a long time, but the internet has certainly helped them gain a lot more popularity. Solving puzzles has always been a fun activity due to the sense of accomplishment you get when you finally solve something, and it's always interesting to see who among you and your friends is the "best" at getting them right.

What's even cooler is that different puzzles test different skills, so there's always a chance that a particular puzzle happens to require a skill set that you're naturally more adept at. This puzzle, for instance, requires mathematical thought as well as analytical skills.

At first glance, a lot of folks are really thrown off by this equation, because it simply does not add up to the math we've learned as kids. Everyone knows 1+5 = 6 so what's going on here? Take another look at the puzzle above and really think about it before reading on to get the answer.

Ok, so here's what's going on: the last number is 72. This can be calculated in a number of different ways.

Method 1: If you look at the sum of the actual numbers (1+5 = 6, 2+10 = 12, and so on) you will notice that the sums that we've been given are all simply three times bigger than the actual sums (6*3 = 18, 12*3 = 36). So, if 4+20 = 24, then the solution to our equation is 24*3 = 72.

Method 2: You could also just look at the end results of the riddle and examine the relationships between them. For instance, 18 = 9*2, 36 = 9*4, and 54 = 9*6. Each is a multiple of nine that goes up by two more each time. By this logic, the next number should be 9*8 = 72.

Alternatively, you can also see that from 18 to 36 to 54, there is a jump of 18 each time: 18+18 = 36, 36+18 = 54. So, to get the final number, we simply calculate 54+18 =72.

This puzzle has been circulating the internet for a while, and it has confounded a lot of people on the way. Were you able to solve it? What method did you find worked best for you? Let us know in the comments.

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H/T: AWM