Identify the incorrect term in the numerical sequence provided below.
6, 19, 58, 124, 214, 331, 474
Correct Answer :
124
Solution :
The correct answer is 124.
To find the incorrect term in the numerical sequence, let us analyze the differences between consecutive terms in the given sequence:
6, 19, 58, 124, 214, 331, 474
Step 1: Calculate the first differences between consecutive terms.
19 - 6 = 13
58 - 19 = 39
124 - 58 = 66
214 - 124 = 90
331 - 214 = 117
474 - 331 = 143
Step 2: Identify the pattern in the differences.
Looking at the differences: 13, 39, ..., ..., 117, 143
Notice that 13, 39, 117, and 143 are all multiples of 26 apart (or multiples of 13):
13 = 13 × 1
39 = 13 × 3
117 = 13 × 9
143 = 13 × 11
The second differences between these valid terms are constant (equal to 26):
39 - 13 = 26
143 - 117 = 26
Therefore, the sequence of first differences should increase by 26 at each step:
1st difference: 13
2nd difference: 13 + 26 = 39
3rd difference: 39 + 26 = 65
4th difference: 65 + 26 = 91
5th difference: 91 + 26 = 117
6th difference: 117 + 26 = 143
Step 3: Reconstruct the correct sequence using the valid differences.
1st term: 6
2nd term: 6 + 13 = 19
3rd term: 19 + 39 = 58
4th term (correct): 58 + 65 = 123
5th term: 123 + 91 = 214
6th term: 214 + 117 = 331
7th term: 331 + 143 = 474
Comparing the given sequence with the correct sequence, the 4th term given is 124 instead of 123.
Hence, 124 is the incorrect term in the sequence.
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