If two unbiased coins are tossed, then what is the probability of having at least one head?

The correct option is 0.75.

To find the probability of obtaining at least one head when two unbiased coins are tossed, we can analyze the possible outcomes step-by-step.

Step 1: Identify the sample space (total possible outcomes)
When a single unbiased coin is tossed, the possible outcomes are Head (H) or Tail (T).
When two unbiased coins are tossed together, the set of all possible outcomes, known as the sample space (S), is:
S = {HH, HT, TH, TT}
where:
• HH means both coins show heads.
• HT means the first coin shows a head and the second shows a tail.
• TH means the first coin shows a tail and the second shows a head.
• TT means both coins show tails.

The total number of possible outcomes is 4.

Step 2: Identify the favorable outcomes
We are looking for the event of getting "at least one head". This means we can have 1 head or 2 heads. Looking at our sample space, the outcomes that satisfy this condition are:
• HH (contains 2 heads)
• HT (contains 1 head)
• TH (contains 1 head)

Therefore, the favorable outcomes are {HH, HT, TH}, and the number of favorable outcomes is 3.

Step 3: Calculate the probability
The probability of an event is calculated as the ratio of the number of favorable outcomes to the total number of outcomes.

$$\text{Probability}=\frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}}$$

Substituting the values into the formula:

$$\text{Probability}=\frac{3}{4}=0.75$$

Hence, the probability of getting at least one head when two unbiased coins are tossed is 0.75.