Multiple choice

Directions: A series is given with one term missing. Choose the correct alternative that will complete the series. ?, 9, 19, 39, 79

  1. 4

  2. 9

  3. 7

  4. 6
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A Correct answer
Explanation

The pattern of the series is that each term is obtained by multiplying the previous term by 2 and adding 1. Working backward from 9, we solve the equation 2x + 1 = 9, which gives x = 4.

AI explanation

The pattern in the sequence multiplies the previous term by 2 and then adds 1 to get the next term. Working backwards from the first known term of 9, we subtract 1 to get 8, and then divide by 2 to find the missing number. Calculating 8 divided by 2 gives the result 4.

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