The average of twelve numbers is 25. If each number is increased by 6, then the new average will be:

A basic property of averages states that if a constant value k is added to every single data value in a set, the arithmetic mean of the dataset also increases exactly by that constant value k.
Given:

Old average =25

Value added to each number (k) =6

Therefore, the new average is:

New Average=Old Average+6
New Average=25+6=31