Brain Test 5 Level 27

Overview

A keypad presents letter-algebra equations, and you must derive each letter's value from the given relations before entering the number each target expression equals. The shown relations include a = 1, ab = 4, bc = 3, and bcd = 0, while the crossed-out equations can change between rounds, so the exact digits for later rounds follow the working shown on the board.

• Difficulty: Hard
• Estimated moves: 3

Step-by-Step Solution

1. Start from the simplest given relation, a = 1, so you have one fixed letter value before touching the expressions that combine letters.
2. Use ab = 4 to solve for the next unknown. With a already known, divide the product by that value to find what b represents in this puzzle's notation.
3. Move to bc = 3 and substitute the value you found for b, leaving c to be solved from that relation.
4. Check the combined relation bcd = 0 against the values you have derived, confirming the letters hold consistently before you read the target expression.
5. Substitute the letter values into the expression the keypad asks for, compute the resulting number, and enter it on the keypad; repeat the derivation if the crossed-out equations change in a later round.
6. Write down each letter value as you derive it, so a later expression can substitute known numbers instead of being solved from scratch; keeping a running note prevents mixing b and c between equations.
7. When the crossed-out equations change between rounds, re-read the active target before entering a digit; a value computed for a previous screen may no longer match the expression now shown on the keypad.

Strategy & Reasoning

The level treats adjacent letters in an expression as a combined product rather than a two-digit number, which is why you solve each unknown from the relations already proven. Working in order from the single-letter equation to the two-letter and three-letter ones keeps the substitutions valid; jumping straight to the long combined expression forces you to guess at letters that have not been solved yet.
The crossed-out equations are the part to watch between rounds. Which expression is struck out can change, so the value you compute for one screen may not match the next screen's target even if the letter relations stay similar. Re-reading the active equation after a round transition avoids entering a leftover digit. Once all three letter values are known, the target expression is just substitution and arithmetic, and the keypad entry confirms the computed number rather than any hidden letter guess.

Tips & Common Mistakes

• Solve the letters in dependency order: fix a first, then derive b and c from the two-letter products.
• Treat adjacent letters as multiplied values here; do not read them as digits of a two-digit number.
• Re-check the active expression after any round changes, since the crossed-out equations may swap the target you must enter.