How long boil potatoes til soft?

depends what you are cooking them for...mashed or potato salad

Approximately 10 to 25 minutes at a high boil. The time required to boil potatoes depends on whether and how the potatoes are cut up. Smaller pieces, such as cubes, expose more surface area to the...

Boil them long enough that a fork will enter them without much effort.

This depends on how small they have been cut. You will know they are done if they are fork tender.

Same as with potatoes. When you stick a fork in the sweet potato and it removes very easily, it's ready. Time depends on size.