Number Series Wrong Number Identification

The question asks to find the incorrect number in the given number series: 9, 19, 39, 78, 159, 319.

Pattern Identification

Let's analyze the relationship between consecutive numbers to find the pattern:

• The first term is 9.
• The second term is 19. The relationship could be multiplication and addition.

Consider the pattern:

Applying the Pattern

1. Check the first transition (9 to 19): $(9 \times 2) + 1 = 18 + 1 = 19$ This matches the second term.
2. Check the second transition (19 to 39): $(19 \times 2) + 1 = 38 + 1 = 39$ This matches the third term.
3. Check the third transition (39 to 78): $(39 \times 2) + 1 = 78 + 1 = 79$ The series contains 78, not 79. This indicates that 78 is the incorrect number.
4. Verify the subsequent terms assuming the correct number after 39 should be 79: Check the fourth transition (assuming 79 to 159): $(79 \times 2) + 1 = 158 + 1 = 159$ This matches the fourth term in the series (which is the term after 78).
5. Check the final transition (159 to 319): $(159 \times 2) + 1 = 318 + 1 = 319$ This matches the last term.

Conclusion

The number 78 breaks the established pattern. Based on the pattern $(\text{Previous Term} \times 2) + 1$, the number should have been 79 instead of 78.

Therefore, the WRONG number in the series is 78.