Directions: In the following number series one number is wrong. Find out the wrong number. 20, 30, 48, 56, 72, 90
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72
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90
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48
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56
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30
The sequence is 20 (+10) = 30, 30 (+18) = 48, 48 (+8) = 56, 56 (+16) = 72, 72 (+18) = 90. The pattern of differences is 10, 18, 8, 16, 18. If the series were 20, 32, 44, 56, 68, 80 or similar, it would be consistent. However, looking at the differences: 10, 18, 8, 16, 18, the number 48 is the outlier that breaks the progression.
The series follows a pattern based on the sum of a number and its reversed form. The numbers are 11, 13, 15, 17, 19, 21, 23, 25, and so on. Taking the number 13, adding it to its reverse 31 gives 44, which is not in the series, but checking the first term: the number 20 plus 02 equals 22, but the series gives 30. The correct pattern is that the terms are the sum of consecutive prime numbers multiplied by 2, but checking the differences: the difference between 30 and 20 is 10, the difference between 48 and 30 is 18, the difference between 56 and 48 is 8, the difference between 72 and 56 is 16, and the difference between 90 and 72 is 18. The term 48 should be 50 to maintain the proper additive sequence, making 48 the wrong number.