The fraction 12/42 is equal to 28.57% when converted to a percentage. This means that if you had 42 items and selected 12 of them, you'd have chosen about 28.57% of the total. It's a fairly small percentage, just over a quarter of the whole.
In everyday situations, you might encounter this fraction or percentage in various contexts. For example, if 12 out of 42 students in a class got an A on a test, you could say that 28.57% of the class aced it. Or if you completed 12 out of 42 tasks on your to-do list, you'd have finished 28.57% of your work. It's a useful number to know for quick mental calculations when dealing with groups of 42 or multiples thereof.
