Medium
Find the wrong term in the series: 1, 7, 13, 17, 25
Explanation
Explanation
Check the differences: 7-1=6, 13-7=6, 17-13=4, 25-17=8. The first two gaps are +6, suggesting the series should keep increasing by 6 each time: 1, 7, 13, 19, 25. Comparing this to the given series, '17' has taken the place of what should be '19'. So 17 is the wrong term, option (3).
PRO TIP
Re-check your working by substituting the answer back into the original question.