Brain Out Level 155

Overview

A list of odd numbers, 1, 3, 5, 7, 9, 11, 13, and 15, sits above three blank boxes with a plus sign between them and a total of 30. Adding three ordinary odd numbers can never reach an even 30, so one number has to be changed by rotation before the sum works. The solution turns the 9 upside down into a 6, then combines 13, 11, and 6 to make 30.
The listed numbers are all odd, and the target 30 is even, which shows the ordinary sum of three odds can never reach the required total.

• Difficulty: Regular
• Estimated moves: 3

Step-by-Step Solution

1. Read the boxes and the target total: three numbers must add to 30. Note that every listed number is odd, and three odds cannot sum to an even result by themselves.
2. Find the digit 9 in the list and rotate it 180 degrees on screen so it turns into the digit 6.
3. Select 13 for the first box, 11 for the second, and the rotated 6 for the third.
4. Check the sum: 13 plus 11 plus 6 equals 30, matching the target.
5. Confirm the filled equation. The level accepts the combination once the rotated 6 is included.

Find the 9 in the list and rotate it 180 degrees so it reads as a 6, which changes its parity and breaks the odd-only impasse. Place 13 in the first box, 11 in the second, and the rotated 6 in the third, then check that 13 plus 11 plus 6 equals 30. Confirm the filled equation once the even result matches the target. If the boxes still hold three odd numbers, the 9 has not been rotated yet, so redo that step before submitting.

After rotating the 9 into a 6, place that transformed digit in one of the three boxes along with 13 and 11, and re-add the trio to confirm it reaches exactly 30. Keep the remaining odd numbers out of the equation, since adding another odd would push the total away from the even target the boxes require.

Strategy & Reasoning

The parity trap is the core of the puzzle: three odd numbers always produce an odd total, so an even 30 seems impossible until one number is flipped. Rotating the 9 into a 6 changes its parity to even, which lets the remaining two odd numbers pair with it to reach an even sum. The chosen 13, 11, and 6 are then the standard valid combination, proving that the trick lies in transforming a displayed number rather than finding a hidden arithmetic rule. The parity trap is the core insight: three odd numbers always sum to an odd result, so an even 30 demands one transformed number. Flipping 9 into 6 supplies that even value, and the 13, 11, 6 combination is the standard valid trio once the rotation has been applied.

Tips & Common Mistakes

• Rotate the 9 upside down to make a 6; this breaks the odd-number impasse.
• Use 13, 11, and the rotated 6 together, since that trio sums to 30.
• Do not keep three odd numbers in the boxes; their total can never equal the even 30.