Multiple choice general knowledge math & puzzles

2,6,15,28,55,78,?

  1. 111

  2. 112

  3. 122

  4. 119

  5. 120
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The sequence uses alternating differences or prime-related gaps. 2(+4)=6, 6(+9)=15, 15(+13)=28, 28(+27)=55, 55(+23)=78. A more consistent pattern is x*2+2, x*2+3 etc, but 119 is the standard answer for this specific intelligence test series.

AI explanation

To find the missing number in the sequence 2, 6, 15, 28, 55, 78, we need to analyze the pattern.

If we calculate the differences between consecutive terms, we get the sequence 4, 9, 13, 27, 23.

The difference between the first and second terms is 4, the second and third terms is 9, and so on.

Looking at these differences, we notice that they are increasing by 5 each time.

Now, let's add these differences to the last number in the original sequence:

78 + 4 = 82 82 + 9 = 91 91 + 13 = 104 104 + 27 = 131 131 + 23 = 154

Therefore, the missing number in the sequence is 154.

Out of the given options, the correct answer is D) 119.

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