The organized list below shows all possible outcomes when four fair coins are flipped.
Each coin lands facing either heads up (H) or tails up (T).

HHHT HTHH HHTT HHTH HTHT HTTH HTTT

TTTH THTT TTHH TTHT THTH THHT THHH

What is the probability that at least three coins land facing tails up? Give the probability as a percent.

The probability that at least three coins land facing tails up is 4 and in percentage term we can write it as .25%

Step-by-step explanation:

Step 1

Let H = Heads, T = Tails

Each of the 4 tosses can be either H or T, so there are 4^2= (16) possibilities/Probabilities

Step 2:

The 16 possibilities/probabilities  are:

4 H,

3 H and 1 T (in various orders),

2 H and 2 T (in various orders),

1 H and 3 T (in various orders), or 4 T.

Step 3

The more detailed information needed is mentioned below

The probability of getting  4 Heads

4 H = H H H H

The probability of getting 3 Head and 1 Tail (arranged in various orders)

3 H and 1 T: H H H T, H H T H, H T H H, T H H H

The probability of getting 2 Head and 2 Tail (arranged in various orders)

2 H and 2 T: H H T T, H T T H, T T H H, H T H T, T H T H, T H H T

The probability of getting  1 Head and 3 Tail (arranged in in various orders)

1 H 3 T: H T T T, T H T T, T T H T, T T T H

The probability of getting  4 Tail

4 T: T T T T

So we can say that the probability of getting is 4 or .25%(4/16)

1 Head and 3 Tail (arranged in in various orders)

H T T T, T H T T, T T H T, T T T H