Tricky Test 2 Level 91

Overview

The level is titled "Find y". Four small triangles are arranged in a 2x2 grid on a dark grey background. Each triangle has a number at its top vertex, a number at its bottom-left vertex, a number at its bottom-right vertex, and a number in the centre circle. The top-left (orange) triangle shows top 5, left 2, right 2, centre 6. The top-right (green) triangle shows top 7, left 5, right 3, centre 6. The bottom-left (blue) triangle shows top 7, left 4, right 2, centre 6. The bottom-right (red) triangle shows top 6, left 5, right 3, and its centre is the unknown "y". At the bottom of the screen is a number picker with a minus button, a plus button, a central number display, and an OK button. The task is to deduce the arithmetic rule linking the three outer numbers to the centre number and apply it to the red triangle.

• Difficulty: Hard
• Estimated moves: 3

Step-by-Step Solution

1. Study the three solved triangles to find the rule. Look at the green triangle: outer numbers 7 (top), 5 (left), 3 (right), centre 6. Try subtracting the left vertex from the top vertex and multiplying by the right vertex: (7 - 5) x 3 = 2 x 3 = 6. This matches the centre.
2. Confirm the rule on the blue triangle: outer numbers 7 (top), 4 (left), 2 (right), centre 6. Apply (top - left) x right: (7 - 4) x 2 = 3 x 2 = 6. This also matches.
3. Confirm on the orange triangle: outer numbers 5 (top), 2 (left), 2 (right), centre 6. Apply (5 - 2) x 2 = 3 x 2 = 6. Matches again. The rule is centre = (top - left) x right.
4. Apply the rule to the red triangle: top = 6, left = 5, right = 3. Compute (6 - 5) x 3 = 1 x 3 = 3.
5. Use the minus/plus buttons at the bottom to set the central number picker to 3, then tap OK. The game confirms the formula "(6 - 5) x 3 = 3" on screen and clears the level.

Strategy & Reasoning

This is a number-pattern puzzle disguised as four separate diagrams. The key is that the same arithmetic rule must hold for all three solved triangles, so you can test candidate operations against them. Adding all three outer numbers together fails because the sums differ (12, 15, 13) while all centres are 6. Multiplying the outer numbers also fails. The operation that works consistently is the combination of a subtraction (top minus left) followed by a multiplication by the right vertex.

Once the rule is established on two or three examples, applying it to the red triangle is mechanical. The trap is that many players waste time trying addition or division patterns because the numbers are small, but those do not generalise across all three triangles. The game even reveals the formula "(6 - 5) x 3 = 3" after you enter 3, confirming the intended rule.

Trying to guess y by looking only at the red triangle is unreliable because there is not enough information; you must use the three solved triangles to reverse-engineer the formula first.

Tips & Common Mistakes

• Mistake: Adding the three outer numbers and trying to divide. Correct approach: The rule is (top - left) x right, not a sum.
• Mistake: Guessing a number and tapping OK without checking it against the solved triangles. Correct approach: Test the rule on at least two of the completed triangles before entering y.
• Mistake: Mixing up which vertex is subtracted from which. Correct approach: Always subtract the bottom-left number from the top number, then multiply by the bottom-right number.
• Mistake: Expecting the answer to be 6 like the other centres. Correct approach: The red triangle has different outer numbers, so y is 3, not 6.