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Q.

3,9,21,45,_

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a

56

b

93

c

66

d

76

answer is C.

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Detailed Solution

e Number Sequence: 3, 9, 21, 45, ?

To determine the next number in the sequence, we observe the pattern in the differences between consecutive terms:

  • 9 - 3 = 6
  • 21 - 9 = 12
  • 45 - 21 = 24

These differences are: 6, 12, and 24, each doubling the previous difference. This suggests that the sequence follows a pattern where each term is obtained by adding twice the previous difference to the current term.

To find the next term:

  • Next difference: 24 × 2 = 48
  • Next term: 45 + 48 = 93

Therefore, the next number in the sequence is 93.

Solution Explanation:

The sequence follows a pattern where each term is obtained by adding twice the previous difference to the current term. This can be represented by the recursive formula:

an = an-1 + 2 × (an-1 - an-2)

Applying this formula:

  • a1 = 3
  • a2 = 9
  • a3 = 21
  • a4 = 45
  • a5 = 45 + 2 × (45 - 21) = 45 + 2 × 24 = 45 + 48 = 93

Thus, the next number is 93.

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