Directions: Find the wrong number in the series. 789, 645, 545, 481, 440, 429, 425

### Concept & Logic Analyze the differences between consecutive terms. If the series decreases rapidly, check if the differences form a recognizable sequence like perfect squares. ### Step-by-Step Solution 1. Calculate the differences between consecutive terms: $789 - 645 = 144$ $645 - 545 = 100$ $545 - 481 = 64$ 2. Observe the sequence of differences: $144, 100, 64$. These are perfect squares of even numbers: $12^2, 10^2, 8^2$. 3. The next difference should be $6^2 = 36$. 4. Let's calculate the expected next term: $481 - 36 = 445$. 5. The term given in the series is $440$. This is the likely error. 6. Verify this by continuing the pattern with the expected term ($445$): Next difference should be $4^2 = 16$. $445 - 16 = 429$. Matches the next term! Next difference should be $2^2 = 4$. $429 - 4 = 425$. Matches the final term! 7. The pattern holds perfectly. The incorrect term is $440$. ### Exam Strategy & Shortcut When you see numbers like $144, 100, 64$ as differences, immediately write down the remaining squares ($36, 16, 4$) and test them to pinpoint the exact wrong number without doing excessive trial and error. ### Common Pitfall Miscalculating a basic subtraction which throws off the pattern recognition. Always double-check your initial differences. ### Final Answer Therefore, the correct answer is **440**.