Directions: Find out the wrong number in each sequence 22, 33, 66, 99, 121, 279, 594

### Concept & Divisibility by 11 This sequence tests your ability to identify a common factor among a group of numbers. Here, the unifying property is that almost all terms are multiples of $11$. ### Step-by-Step Solution 1. Visually inspect the numbers: $22, 33, 66, 99, 121$. These are highly recognizable multiples of $11$. 2. Test each number for divisibility by $11$: - $22 = 11 \times 2$ - $33 = 11 \times 3$ - $66 = 11 \times 6$ - $99 = 11 \times 9$ - $121 = 11 \times 11$ - $594 \rightarrow 5 - 9 + 4 = 0$ (Divisible by $11$) 3. Now test $279$: - Applying the divisibility rule for $11$ (alternating sum of digits): $2 - 7 + 9 = 4$. - Since $4$ is not $0$ or a multiple of $11$, $279$ is not divisible by $11$. 4. Because it lacks this shared property, $279$ is the wrong number in the sequence. ### Exam Strategy & Shortcut If a sequence starts with $22, 33, 66$, immediately assume an "multiples of $11$" rule. Use the alternating digit sum test (e.g., for $594$: $5+4-9=0$) to rapidly verify larger numbers. ### Common Pitfall Trying to find an arithmetic pattern of differences ($+11, +33, +33, +22...$) which is erratic and will not lead to identifying the true outlier. ### Final Answer Therefore, the correct answer is **279**.