A pattern formed by two characters $a$ and $b$ is repeated more than once in the following string :
$x , b , x , a , x , a , x , x , a , x , a , x , b , a , b$
What is $x , x$ in the 7th and 8th positions from the left in the above string?

Question

A pattern formed by two characters $a$ and $b$ is repeated more than once in the following string :
$x , b , x , a , x , a , x , x , a , x , a , x , b , a , b$
What is $x , x$ in the 7th and 8th positions from the left in the above string?

Accepted Answer

$bb$

Explanation: The string has 15 positions. A pattern repeated more than once with length 5 fits perfectly (repeated 3 times). The last 5 known characters are: a, x, b, a, b. Testing this as the repeating pattern and solving for x values: the pattern must be a, b, b, a, b. Repeating a, b, b, a, b three times gives: a, b, b, a, b, a, b, b, a, b, a, b, b, a, b. Positions 7 and 8 are both b. Therefore, x, x at positions 7 and 8 is bb, making Option 4 the correct answer.

Detailed Explanation:

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