Multiple choice

( \text{In each of these questions a number series is given. In each series, only one number is wrong. Find out the wrong number.} )( 1 \quad 3 \quad 6 \quad 11 \quad 20 \quad 39 \quad 70 )

  1. 3

  2. 39

  3. 11

  4. 20

  5. 6
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The pattern is: ×2+1, ×2+0, ×2-1, ×2-2, ×2-3, ×2-4. Let's verify: 1×2+1=3, 3×2+0=6, 6×2-1=11, 11×2-2=20, 20×2-3=37 (not 39), 37×2-4=70. So 39 is wrong - it should be 37. The subtraction decreases by 1 each time (starts at +1, then 0, -1, -2, -3, -4).

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