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

Courtesy of Puzzles9Can you find the missing number?
  • Puzzles9 shared a brain teaser with three pentagons, each with a set of five numbers.
  • The middle pentagon is missing a number.
  • To fill in the missing number, you must figure out the relationship between the numbers in the pentagons and continue the sequence.
  • Can you solve it? Scroll down for the answer.

This brain-teasing maths 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 maths brain teaserCourtesy of Puzzles9Can you find the missing number?

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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