Correct Answer - Option 5 : 0.5

**Given:**

Two coins are flipped one after another.

**Formula and Concept Used:**

The probability of occurrence of an event E, within a sample space S, is given by:

P(E) = n(E) / n(S)

where P(E) = probability of occurrence of the event E,

n(E) = number of times the event E occurs, and

n(S) = number of points in the sample space S.

In the case of two independent events, the probability of the first event does not affect the probability of the second event.

**Calculation:**

When a coin is tossed, we obtain either head or tail.

∴ n(S) = 2

Number of times head occurs, when a coin is tossed = 1

∴ n(E) = 1

∴ The probability of obtaining a head, when a coin is tossed = 1/2 = 0.5

Similarly, the probability of obtaining a tail = 0.5

But, the tossing of the two coins are independent events, because the outcome of the first experiment doesn't affect the outcome of the second.

**∴ The probability that tail comes up on the second coin, if a head appears on the first coin is 0.5**

**Mistake Point:**

It is important to note here that if the student forgets the concept of independent events, then the answer would be obtained as

0.5 × 0.5 = 0.25,

which is wrong.

Hence, it is important to note that both these events are independent of each other.