Multiple choice

Directions for questions 15 and 16: Select the correct alternative from the given ones that will complete the series. 5,11,21,43,85,?

  1. 170

  2. 171

  3. 181

  4. 185
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The pattern is: 5*2+1=11, 11*2-1=21, 21*2+1=43, 43*2-1=85, 85*2+1=171.

AI explanation

The series follows a pattern where each term is multiplied by 2, and then 1 is alternately added and subtracted. For example, $5 \times 2 + 1 = 11$, $11 \times 2 - 1 = 21$, and $21 \times 2 + 1 = 43$. Applying this to the last term gives $85 \times 2 + 1 = 171$. The result is 171.

Keep practicing — related questions