Multiple choice general knowledge math & puzzles

A number of the form 213ab, where a and b are digits, has a reminder less than 10 when divided by 100. The sum of all the digits in the above number is equal to 13. Find the digit b.

  1. 7

  2. 6

  3. 8

  4. 10
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A Correct answer
Explanation

A remainder $< 10$ when divided by 100 means the tens digit 'a' must be 0. The number is $2130b$. The sum of digits is $2+1+3+0+b = 6+b$. If the sum is 13, then $6+b=13$, so $b=7$.

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