This math puzzle is about a pyramid made up of consecutive integers starting from 1. So on the first row, we have 1. On the second row, we have 2, 3 and 4.

There are two more numbers in every subsequent row. And our goal is to find the number directly below the number 400.

As usual, give this problem a try. And when you are ready, keep reading for the solution.

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Solution

Let’s cut to the chase and notice that the number on the right side of every row is a square number.

1 is 1^2. 4 is 2^2. 9 is 3^2. 16 is 4^2.

In general this pattern holds true for any arbitrary row, so on the nth row, the number on the right must be n^2.

400 is (20)^2. And 441 is (21)^2.

Now we clearly see that the number below 400 is 440.