Question

Which of the following cannot be the probability of an event?
A. \[\dfrac{2}{3}\]
B. \[ - 1.5\]
C. \[15\% \]
D. \[0.7\]

Answer 1

Hint: We have to find the option that cannot be the probability of an event. To solve that we need to know the definition of probability.
Probability means possibility. It is a branch of mathematics that deals with the occurrence of a random event. Probability has been introduced in Maths to predict how likely events are to happen.

Complete step-by-step answer:
To find the answer, we need to know the definition of probability.
Probability is a measure of the likelihood of an event to occur. Many events cannot be predicted with total certainty. We can predict only the chance of an event to occur i.e. how likely they are to happen, using it. Probability can range in from 0 to 1, where 0 means the event to be an impossible one and 1 indicates a certain event. The probability of all the events in a sample space adds up to 1.
\[{\mathbf{Probability}}{\text{ }}{\mathbf{of}}{\text{ }}{\mathbf{event}}{\text{ }}{\mathbf{to}}{\text{ }}{\mathbf{happen}} = \dfrac{{{\mathbf{Number}}{\text{ }}{\mathbf{of}}{\text{ }}{\mathbf{favourable}}{\text{ }}{\mathbf{outcomes}}}}{{{\mathbf{Total}}{\text{ }}{\mathbf{Number}}{\text{ }}{\mathbf{of}}{\text{ }}{\mathbf{outcomes}}}}\]
By the definition we can get that, the probability of an event cannot be negative.
Hence, \[ - 1.5\] cannot be considered as probability.

So, the correct answer is “Option B”.

Note: Probability can range in from 0 to 1, where 0 means the event to be an impossible one and 1 indicates a certain event.
It can never be negative.
Let us assume an unbiased coin is tossed. There is an equal chance to get head and tail.
So, the probability of getting a head is \[\dfrac{1}{2}\].
And, the probability of getting a tail is \[\dfrac{1}{2}\].
So, the sum of probability of getting head and tail is \[\dfrac{1}{2} + \dfrac{1}{2} = 1\].