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This brain-teasing math puzzle is missing a number — can you solve it?

pentagon math brain teaser
Can you find the missing number? Courtesy of Puzzles9
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This brain-teasing math problem created by Puzzles9 presents three pentagons, each with a set of five numbers. But here's the catch — the middle pentagon is missing a number in the bottom right corner. 

Can you figure out how all of the numbers are related and fill in the missing one?

Here's the puzzle:

pentagon math brain teaser
Can you find the missing number?  Courtesy of Puzzles9

If you're stumped, don't worry. Here's how to fill in that last number.

From left to right, let's label the pentagons A, B, and C. The difference between the numbers in pentagons A and B can be found in Pentagon C in the same location across the board. In other words, Pentagon B - Pentagon A = Pentagon C.

For example, take the top row of numbers. A = 2, B = 5, and C = 3. Plugging in those numbers to our formula (B - A = C), we get 5 - 2 = 3, which is correct.

Now let's use it to solve for the missing number in pentagon B, the bottom right.

B - A = C

B - 1 = 9

B = 10

The answer is 10.

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Talia Lakritz
Talia Lakritz
Talia Lakritz is a Life correspondent at Business Insider covering politics and power through a visual storytelling lens. She has reported from the White House as well as military installations, mansions, and museums across the country, bringing readers inside fascinating places through immersive features.Previously, she wrote for The New York Jewish Week and SciShow Space.Talia holds a BA in English with a concentration in Creative Writing from Barnard College of Columbia University and ordination as an interfaith minister from One Spirit Learning Alliance. She hopes to one day visit all 50 states and all 14 public presidential libraries.Politics and power:Visual features:Human interest: