Multiple choice general knowledge math & puzzles

A can do a piece of work in 10 days which can be done by B in 12 days. How long would it take to do the work together?

  1. 2 1/11

  2. 4 2/11

  3. 5 5/11

  4. 6 2/11

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A's rate is 1/10 and B's rate is 1/12. Combined rate = 1/10 + 1/12 = (6+5)/60 = 11/60. The time taken together is the reciprocal: 60/11 = 5 5/11 days. Other options represent calculation errors in the common denominator or reciprocal.