Combination Calculator Calculate Combinations. Show Work.

Learn

Probability basics

Probability starts by counting how many outcomes you want and comparing that count to all equally likely outcomes in the sample space.

Core idea

Favorable outcomes divided by total outcomes

For a basic equally likely setup, probability is:

P(E) = favorable outcomes / total outcomes

If 4 cards out of 52 are aces, then the probability of drawing an ace is 4/52, which reduces to 1/13.

Three formats

Fraction, decimal, and percent all mean the same chance

  • 1/13 is the exact fraction.
  • 0.076923 is the decimal form.
  • 7.6923% is the percent form.

Good calculators show all three so you can match the format your class, worksheet, or own preference expects.

What must be true

The outcomes need to be equally likely

The simple favorable-over-total formula works only when every outcome in the sample space is equally likely. Standard card draws and fair coin flips fit that rule. Biased coins or uneven spinners do not.